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Biological effects
The main public concern regarding the ozone hole has been the effects of increased surface UV radiation on human health. So far, ozone depletion in most locations has been typically a few percent and, as noted above, no direct evidence of health damage is available in most latitudes. If the high levels of depletion seen in the ozone hole were to be common across the globe, the effects could be substantially more dramatic. As the ozone hole over Antarctica has in some instances grown so large as to affect parts of Australia, New Zealand, Chile, Argentina, and South Africa, environmentalists have been concerned that the increase in surface UV could be significant. Excessive ultraviolet radiation (UVR) has reducing effects on the rates of photosynthesis and growth of benthic diatom communities (microalgae species that increase water quality and are pollution resistant) that are present in shallow freshwater. Ozone depletion not only affects human health but also has a profound impact on biodiversity. It damages plants and trees at the cellular level, affecting their growth, vitality, photosynthesis, water balance, and defense mechanisms against pests and diseases. This sets off a cascade of ecological impacts, harming soil microbes, insects, wildlife, and entire ecosystems.
Ozone depletion would magnify all of the effects of UV on human health, both positive (including production of vitamin D) and negative (including sunburn, skin cancer, and cataracts). In addition, increased surface UV leads to increased tropospheric ozone, which is a health risk to humans.
Basal and squamous cell carcinomas
The most common forms of skin cancer in humans, basal and squamous cell carcinomas, have been strongly linked to UV-B exposure. The mechanism by which UVB induces these cancers is well understood—absorption of UV-B radiation causes the pyrimidine bases in the DNA molecule to form dimers, resulting in transcription errors when the DNA replicates. These cancers are relatively mild and rarely fatal, although the treatment of squamous cell carcinoma sometimes requires extensive reconstructive surgery. By combining epidemiological data with results of animal studies, scientists have estimated that every one percent decrease in long-term stratospheric ozone would increase the incidence of these cancers by 2%. | Ozone depletion | Wikipedia | 477 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
Melanoma
Another form of skin cancer, Melanoma, is much less common but far more dangerous, being lethal in about 15–20 percent of the cases diagnosed. The relationship between melanoma and ultraviolet exposure is not yet fully understood, but it appears that both UV-B and UV-A are involved. Because of this uncertainty, it is difficult to estimate the effect of ozone depletion on melanoma incidence. One study showed that a 10 percent increase in UV-B radiation was associated with a 19 percent increase in melanomas for men and 16 percent for women. A study of people in Punta Arenas, at the southern tip of Chile, showed a 56 percent increase in melanoma and a 46 percent increase in non-melanoma skin cancer over a period of seven years, along with decreased ozone and increased UVB levels.
Cortical cataracts
Epidemiological studies suggest an association between ocular cortical cataracts and UV-B exposure, using crude approximations of exposure and various cataract assessment techniques. A detailed assessment of ocular exposure to UV-B was carried out in a study on Chesapeake Bay Watermen, where increases in average annual ocular exposure were associated with increasing risk of cortical opacity. In this highly exposed group of predominantly white males, the evidence linking cortical opacities to sunlight exposure was the strongest to date. Based on these results, ozone depletion is predicted to cause hundreds of thousands of additional cataracts by 2050.
Increased tropospheric ozone
Increased surface UV leads to increased tropospheric ozone. Ground-level ozone is generally recognized to be a health risk, as ozone is toxic due to its strong oxidant properties. The risks are particularly high for young children, the elderly, and those with asthma or other respiratory difficulties. At this time, ozone at ground level is produced mainly by the action of UV radiation on combustion gases from vehicle exhausts. | Ozone depletion | Wikipedia | 406 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
Increased production of vitamin D
Vitamin D is produced in the skin by ultraviolet light. Thus, higher UVB exposure raises human vitamin D in those deficient in it. Recent research (primarily since the Montreal Protocol) shows that many humans have less than optimal vitamin D levels. In particular, in the U.S. population, the lowest quarter of vitamin D (<17.8 ng/ml) were found using information from the National Health and Nutrition Examination Survey to be associated with an increase in all-cause mortality in the general population. While blood level of vitamin D in excess of 100 ng/ml appear to raise blood calcium excessively and to be associated with higher mortality, the body has mechanisms that prevent sunlight from producing vitamin D in excess of the body's requirements.
Effects on animals
A November 2011 report by scientists at the Institute of Zoology in London, England found that whales off the coast of California have shown a sharp rise in sun damage, and these scientists "fear that the thinning ozone layer is to blame". The study photographed and took skin biopsies from over 150 whales in the Gulf of California and found "widespread evidence of epidermal damage commonly associated with acute and severe sunburn", having cells that form when the DNA is damaged by UV radiation. The findings suggest "rising UV levels as a result of ozone depletion are to blame for the observed skin damage, in the same way that human skin cancer rates have been on the increase in recent decades." Apart from whales many other animals such as dogs, cats, sheep and terrestrial ecosystems also suffer the negative effects of increased UV-B radiations.
Effects on crops
An increase of UV radiation would be expected to affect crops. A number of economically important species of plants, such as rice, depend on cyanobacteria residing on their roots for the retention of nitrogen. Cyanobacteria are sensitive to UV radiation and would be affected by its increase. "Despite mechanisms to reduce or repair the effects of increased ultraviolet radiation, plants have a limited ability to adapt to increased levels of UVB, therefore plant growth can be directly affected by UVB radiation."
Effects on plant life | Ozone depletion | Wikipedia | 438 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
Over the years, the Arctic ozone layer has depleted severely. As a consequence species that live above the snow cover or in areas where snow has melted abundantly, due to hot temperatures, are negatively impacted due to UV radiation that reaches the ground. Depletion of the ozone layer and allowing excess UVB radiation would initially be assumed to increase damage to plant DNA. Reports have found that when plants are exposed to UVB radiation similar to stratospheric ozone depletion, there was no significant change in plant height or leaf mass, but showed a response in shoot biomass and leaf area with a small decrease. However, UVB radiation has been shown to decrease quantum yield of photosystem II. UVB damage only occurs under extreme exposure, and most plants also have UVB absorbing flavonoids which allow them to acclimatize to the radiation present. Plants experience different levels of UV radiation throughout the day. It is known that they are able to shift the levels and types of UV sunscreens (i.e. flavonoids), that they contain, throughout the day. This allows them to increase their protection against UV radiation. Plants that have been affected by radiation throughout development are more affected by the inability to intercept light with a larger leaf area than having photosynthetic systems compromised. Damage from UVB radiation is more likely to be significant on species interactions than on plants themselves.
Another significant impact of ozone depletion on plant life is the stress experienced by plants when exposed to UV radiation. This can cause a decrease in plant growth and an increase in oxidative stress, due to the production of nitric oxide and hydrogen peroxide. In areas where substantial ozone depletion has occurred, increased UV-B radiation reduces terrestrial plant productivity (and likewise carbon sequestration) by about 6%.
Moreover, if plants are exposed to high levels of UV radiation, it can elicit the production of harmful volatile organic compounds, like isoprenes. The emission of isoprenes into the air, by plants, can severely impact the environment by adding to air pollution and increasing the amount of carbon in the atmosphere, ultimately contributing to climate change.
Public policy | Ozone depletion | Wikipedia | 443 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
The full extent of the damage that CFCs have caused to the ozone layer is not known and will not be known for decades; however, marked decreases in column ozone have already been observed. The Montreal and Vienna conventions were installed long before a scientific consensus was established or important uncertainties in the science field were being resolved. The ozone case was understood comparably well by lay persons as e.g. Ozone shield or ozone hole were useful "easy-to-understand bridging metaphors". Americans voluntarily switched away from aerosol sprays, resulting in a 50 percent sales loss even before legislation was enforced.
After a 1976 report by the United States National Academy of Sciences concluded that credible scientific evidence supported the ozone depletion hypothesis a few countries, including the United States, Canada, Sweden, Denmark, and Norway, moved to eliminate the use of CFCs in aerosol spray cans. At the time this was widely regarded as a first step towards a more comprehensive regulation policy, but progress in this direction slowed in subsequent years, due to a combination of political factors (continued resistance from the halocarbon industry and a general change in attitude towards environmental regulation during the first two years of the Reagan administration) and scientific developments (subsequent National Academy assessments that indicated that the first estimates of the magnitude of ozone depletion had been overly large).
A critical DuPont manufacturing patent for Freon was set to expire in 1979. The United States banned the use of CFCs in aerosol cans in 1978. The European Community rejected proposals to ban CFCs in aerosol sprays, and in the U.S., CFCs continued to be used as refrigerants and for cleaning circuit boards. Worldwide CFC production fell sharply after the U.S. aerosol ban, but by 1986 had returned nearly to its 1976 level. In 1993, DuPont Canada closed its CFC facility.
The U.S. government's attitude began to change again in 1983, when William Ruckelshaus replaced Anne M. Burford as Administrator of the United States Environmental Protection Agency (EPA). Under Ruckelshaus and his successor, Lee Thomas, the EPA pushed for an international approach to halocarbon regulations. In 1985 twenty nations, including most of the major CFC producers, signed the Vienna Convention for the Protection of the Ozone Layer, which established a framework for negotiating international regulations on ozone-depleting substances. That same year, the discovery of the Antarctic ozone hole was announced, causing a revival in public attention to the issue. | Ozone depletion | Wikipedia | 511 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
In 1987, representatives from 43 nations signed the Montreal Protocol. Meanwhile, the halocarbon industry shifted its position and started supporting a protocol to limit CFC production. However, this shift was uneven with DuPont acting more quickly than its European counterparts. DuPont may have feared court action related to increased skin cancer, especially as the EPA had published a study in 1986 claiming that an additional 40 million cases and 800,000 cancer deaths were to be expected in the U.S. in the next 88 years. The EU shifted its position as well after Germany gave up its defence of the CFC industry and started supporting moves towards regulation. Government and industry in France and the UK tried to defend their CFC producing industries even after the Montreal Protocol had been signed.
At Montreal, the participants agreed to freeze production of CFCs at 1986 levels and to reduce production by 50 percent by 1999. After a series of scientific expeditions to the Antarctic produced convincing evidence that the ozone hole was indeed caused by chlorine and bromine from manmade organohalogens, the Montreal Protocol was strengthened at a 1990 meeting in London. The participants agreed to phase out CFCs and halons entirely (aside from a very small amount marked for certain "essential" uses, such as asthma inhalers) by 2000 in non-Article 5 countries and by 2010 in Article 5 (less developed) signatories. At a 1992 meeting in Copenhagen, Denmark, the phase-out date was moved up to 1996. At the same meeting, methyl bromide (MeBr), a fumigant used primarily in agricultural production, was added to the list of controlled substances. For all substances controlled under the protocol, phaseout schedules were delayed for less developed ('Article 5(1)') countries, and phaseout in these countries was supported by transfers of expertise, technology, and money from non-Article 5(1) Parties to the Protocol. Additionally, exemptions from the agreed schedules could be applied for under the Essential Use Exemption (EUE) process for substances other than methyl bromide and under the Critical Use Exemption (CUE) process for methyl bromide. | Ozone depletion | Wikipedia | 430 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
Civil society, including especially non-governmental organizations (NGOs), played critical roles at all stages of policy development leading to the Vienna Conference, the Montreal Protocol, and in assessing compliance afterwards. The major companies claimed that no alternatives to HFC existed. An ozone-safe hydrocarbon refrigerant was developed at a technological institute in Hamburg, Germany, consisting of a mixture of the hydrocarbon gases propane and butane, and in 1992 came to the attention of the NGO Greenpeace. Greenpeace called it "Greenfreeze". The NGO then worked successfully first with a small and struggling company to market an appliance beginning in Europe, then Asia and later Latin America, receiving a 1997 UNEP award. By 1995, Germany had made CFC refrigerators illegal. Since 2004, corporations like Coca-Cola, Carlsberg, and IKEA formed a coalition to promote the ozone-safe Greenfreeze units. Production spread to companies like Electrolux, Bosch, and LG, with sales reaching some 300 million refrigerators by 2008. In Latin America, a domestic Argentinian company began Greenfreeze production in 2003, while the giant Bosch in Brazil began a year later. By 2013 it was being used by some 700 million refrigerators, making up about 40 percent of the market.
In the U.S., however, change has been much slower. To some extent, CFCs were being replaced by the less damaging hydrochlorofluorocarbons (HCFCs), although concerns remain regarding HCFCs also. In some applications, hydrofluorocarbons (HFCs) were being used to replace CFCs. HFCs, which contain no chlorine or bromine, do not contribute to ozone depletion although they are potent greenhouse gases. The best known of these compounds is probably HFC-134a (R-134a), which in the United States has largely replaced CFC-12 (R-12) in automobile air conditioners. In laboratory analytics (a former "essential" use) the ozone depleting substances can be replaced with other solvents. Chemical companies like Du Pont, whose representatives disparaged Greenfreeze as "that German technology," maneuvered the EPA to block the technology in the U.S. until 2011. Ben & Jerry's of Unilever and General Electric, spurred by Greenpeace, had expressed formal interest in 2008 which figured in the EPA's final approval. | Ozone depletion | Wikipedia | 507 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
The EU recast its Ozone Regulation in 2009. The law bans ozone-depleting substances with the goal of protecting the ozone layer. The list of ODS that are subject to the regulation is the same as those under the Montreal Protocol, with some additions.
More recently, policy experts have advocated for efforts to link ozone protection efforts to climate protection efforts. Many ODS are also greenhouse gases, some thousands of times more powerful agents of radiative forcing than carbon dioxide over the short and medium term. Thus policies protecting the ozone layer have had benefits in mitigating climate change. The reduction of the radiative forcing due to ODS probably masked the true level of climate change effects of other greenhouse gases, and was responsible for the "slow down" of global warming from the mid-90s. Policy decisions in one arena affect the costs and effectiveness of environmental improvements in the other.
ODS requirements in the marine industry
The IMO has amended MARPOL Annex VI Regulation 12 regarding ozone depleting substances. As from July 1, 2010, all vessels where MARPOL Annex VI is applicable should have a list of equipment using ozone depleting substances. The list should include the name of ODS, type and location of equipment, quantity in kg and date. All changes since that date should be recorded in an ODS Record book on board recording all intended or unintended releases to the atmosphere. Furthermore, new ODS supply or landing to shore facilities should be recorded as well.
Prospects of ozone depletion
Since the adoption and strengthening of the Montreal Protocol has led to reductions in the emissions of CFCs, atmospheric concentrations of the most-significant compounds have been declining. These substances are being gradually removed from the atmosphere; since peaking in 1994, the Effective Equivalent Chlorine (EECl) level in the atmosphere had dropped about 10 percent by 2008. The decrease in ozone-depleting chemicals has also been significantly affected by a decrease in bromine-containing chemicals. The data suggest that substantial natural sources exist for atmospheric methyl bromide (). The phase-out of CFCs means that nitrous oxide (), which is not covered by the Montreal Protocol, has become the most highly emitted ozone-depleting substance and is expected to remain so throughout the 21st century. | Ozone depletion | Wikipedia | 464 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
According to the IPCC Sixth Assessment Report, global stratospheric ozone levels experienced rapid decline in the 1970s and 1980s and have since been increasing, but have not reached preindustrial levels. Although considerable variability is expected from year to year, including in polar regions where depletion is largest, the ozone layer is expected to continue recovering in coming decades due to declining ozone-depleting substance concentrations, assuming full compliance with the Montreal Protocol.
The Antarctic ozone hole is expected to continue for decades. Ozone concentrations in the lower stratosphere over Antarctica increased by 5–10 percent by 2020 and will return to pre-1980 levels by about 2060–2075. This is 10–25 years later than predicted in earlier assessments, because of revised estimates of atmospheric concentrations of ozone-depleting substances, including a larger predicted future usage in developing countries. Another factor that may prolong ozone depletion is the drawdown of nitrogen oxides from above the stratosphere due to changing wind patterns. A gradual trend toward "healing" was reported in 2016. In 2019, the ozone hole was at its smallest in the previous thirty years, due to the warmer polar stratosphere weakening the polar vortex. In September 2023, the Antarctic ozone hole was one of the largest on record, at 26 million square kilometers. The anomalously large ozone loss may have been a result of the 2022 Tonga volcanic eruption.
Research history
The basic physical and chemical processes that lead to the formation of an ozone layer in the Earth's stratosphere were discovered by Sydney Chapman in 1930. Short-wavelength UV radiation splits an oxygen () molecule into two oxygen (O) atoms, which then combine with other oxygen molecules to form ozone. Ozone is removed when an oxygen atom and an ozone molecule "recombine" to form two oxygen molecules, i.e. O + → 2. In the 1950s, David Bates and Marcel Nicolet presented evidence that various free radicals, in particular hydroxyl (OH) and nitric oxide (NO), could catalyze this recombination reaction, reducing the overall amount of ozone. These free radicals were known to be present in the stratosphere, and so were regarded as part of the natural balance—it was estimated that in their absence, the ozone layer would be about twice as thick as it currently is. | Ozone depletion | Wikipedia | 482 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
In 1970 Paul Crutzen pointed out that emissions of nitrous oxide (), a stable, long-lived gas produced by soil bacteria, from the Earth's surface could affect the amount of nitric oxide (NO) in the stratosphere. Crutzen showed that nitrous oxide lives long enough to reach the stratosphere, where it is converted into NO. Crutzen then noted that increasing use of fertilizers might have led to an increase in nitrous oxide emissions over the natural background, which would in turn result in an increase in the amount of NO in the stratosphere. Thus human activity could affect the stratospheric ozone layer. In the following year, Crutzen and (independently) Harold Johnston suggested that NO emissions from supersonic passenger aircraft, which would fly in the lower stratosphere, could also deplete the ozone layer. However, more recent analysis in 1995 by David W. Fahey, an atmospheric scientist at the National Oceanic and Atmospheric Administration, found that the drop in ozone would be from 1–2 percent if a fleet of 500 supersonic passenger aircraft were operated. This, Fahey expressed, would not be a showstopper for advanced supersonic passenger aircraft development.
Rowland–Molina hypothesis
In 1974 Frank Sherwood Rowland, Chemistry Professor at the University of California at Irvine, and his postdoctoral associate Mario J. Molina suggested that long-lived organic halogen compounds, such as CFCs, might behave in a similar fashion as Crutzen had proposed for nitrous oxide. James Lovelock had recently discovered, during a cruise in the South Atlantic in 1971, that almost all of the CFC compounds manufactured since their invention in 1930 were still present in the atmosphere. Molina and Rowland concluded that, like , the CFCs would reach the stratosphere where they would be dissociated by UV light, releasing chlorine atoms. A year earlier, Richard Stolarski and Ralph Cicerone at the University of Michigan had shown that Cl is even more efficient than NO at catalyzing the destruction of ozone. Similar conclusions were reached by Michael McElroy and Steven Wofsy at Harvard University. Neither group, however, had realized that CFCs were a potentially large source of stratospheric chlorine—instead, they had been investigating the possible effects of HCl emissions from the Space Shuttle, which are very much smaller. | Ozone depletion | Wikipedia | 493 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
The Rowland–Molina hypothesis was strongly disputed by representatives of the aerosol and halocarbon industries. The Chair of the Board of DuPont was quoted as saying that ozone depletion theory is "a science fiction tale ... a load of rubbish ... utter nonsense". Robert Abplanalp, the President of Precision Valve Corporation (and inventor of the first practical aerosol spray can valve), wrote to the Chancellor of UC Irvine to complain about Rowland's public statements. Nevertheless, within three years most of the basic assumptions made by Rowland and Molina were confirmed by laboratory measurements and by direct observation in the stratosphere. The concentrations of the source gases (CFCs and related compounds) and the chlorine reservoir species (HCl and ) were measured throughout the stratosphere, and demonstrated that CFCs were indeed the major source of stratospheric chlorine, and that nearly all of the CFCs emitted would eventually reach the stratosphere. Even more convincing was the measurement, by James G. Anderson and collaborators, of chlorine monoxide (ClO) in the stratosphere. ClO is produced by the reaction of Cl with ozone—its observation thus demonstrated that Cl radicals not only were present in the stratosphere but also were actually involved in destroying ozone. McElroy and Wofsy extended the work of Rowland and Molina by showing that bromine atoms were even more effective catalysts for ozone loss than chlorine atoms and argued that the brominated organic compounds known as halons, widely used in fire extinguishers, were a potentially large source of stratospheric bromine. In 1976 the United States National Academy of Sciences released a report concluding that the ozone depletion hypothesis was strongly supported by the scientific evidence. In response the United States, Canada and Norway banned the use of CFCs in aerosol spray cans in 1978. Early estimates were that, if CFC production continued at 1977 levels, the total atmospheric ozone would after a century or so reach a steady state, 15 to 18 percent below normal levels. By 1984, when better evidence on the speed of critical reactions was available, this estimate was changed to 5 to 9 percent steady-state depletion.
Crutzen, Molina, and Rowland were awarded the 1995 Nobel Prize in Chemistry for their work on stratospheric ozone. | Ozone depletion | Wikipedia | 482 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
Antarctic ozone hole
The discovery of the Antarctic "ozone hole" by British Antarctic Survey scientists Farman, Gardiner and Shanklin (first reported in a paper in Nature in May 1985) came as a shock to the scientific community, because the observed decline in polar ozone was far larger than had been anticipated. Satellite measurements (TOMS onboard Nimbus 7) showing massive depletion of ozone around the south pole were becoming available at the same time. However, these were initially rejected as unreasonable by data quality control algorithms (they were filtered out as errors since the values were unexpectedly low); the ozone hole was detected only in satellite data when the raw data was reprocessed following evidence of ozone depletion in in situ observations. When the software was rerun without the flags, the ozone hole was seen as far back as 1976.
Susan Solomon, an atmospheric chemist at the National Oceanic and Atmospheric Administration (NOAA), proposed that chemical reactions on polar stratospheric clouds (PSCs) in the cold Antarctic stratosphere caused a massive, though localized and seasonal, increase in the amount of chlorine present in active, ozone-destroying forms. The polar stratospheric clouds in Antarctica are only formed at very low temperatures, as low as −80 °C, and early spring conditions. In such conditions the ice crystals of the cloud provide a suitable surface for conversion of unreactive chlorine compounds into reactive chlorine compounds, which can easily deplete ozone.
Moreover, the polar vortex formed over Antarctica is very tight and the reaction occurring on the surface of the cloud crystals is far different from when it occurs in atmosphere. These conditions have led to ozone hole formation in Antarctica. This hypothesis was decisively confirmed, first by laboratory measurements and subsequently by direct measurements, from the ground and from high-altitude airplanes, of very high concentrations of chlorine monoxide (ClO) in the Antarctic stratosphere.
Alternative hypotheses, which had attributed the ozone hole to variations in solar UV radiation or to changes in atmospheric circulation patterns, were also tested and shown to be untenable. | Ozone depletion | Wikipedia | 433 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
Meanwhile, analysis of ozone measurements from the worldwide network of ground-based Dobson spectrophotometers led an international panel to conclude that the ozone layer was in fact being depleted, at all latitudes outside of the tropics. These trends were confirmed by satellite measurements. As a consequence, the major halocarbon-producing nations agreed to phase out production of CFCs, halons, and related compounds, a process that was completed in 1996.
Since 1981 the United Nations Environment Programme, under the auspices of the World Meteorological Organization, has sponsored a series of technical reports on the Scientific Assessment of Ozone Depletion, based on satellite measurements. The 2007 report showed that the hole in the ozone layer was recovering and the smallest it had been for about a decade.
A 2010 report found, "Over the past decade, global ozone and ozone in the Arctic and Antarctic regions is no longer decreasing but is not yet increasing. The ozone layer outside the Polar regions is projected to recover to its pre-1980 levels some time before the middle of this century. In contrast, the springtime ozone hole over the Antarctic is expected to recover much later."
In 2012, NOAA and NASA reported "Warmer air temperatures high above the Antarctic led to the second smallest season ozone hole in 20 years averaging 17.9 million square kilometres. The hole reached its maximum size for the season on Sept 22, stretching to 21.2 million square kilometres." A gradual trend toward "healing" was reported in 2016 and then in 2017. It is reported that the recovery signal is evident even in the ozone loss saturation altitudes.
The hole in the Earth's ozone layer over the South Pole has affected atmospheric circulation in the Southern Hemisphere all the way to the equator. The ozone hole has influenced atmospheric circulation all the way to the tropics and increased rainfall at low, subtropical latitudes in the Southern Hemisphere.
Arctic ozone "mini-hole"
On March 3, 2005, the journal Nature published an article linking 2004's unusually large Arctic ozone hole to solar wind activity. | Ozone depletion | Wikipedia | 412 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
On March 15, 2011, a record ozone layer loss was observed, with about half of the ozone present over the Arctic having been destroyed. The change was attributed to increasingly cold winters in the Arctic stratosphere at an altitude of approximately , a change associated with global warming in a relationship that is still under investigation. By March 25, the ozone loss had become the largest compared to that observed in all previous winters with the possibility that it would become an ozone hole. This would require that the quantities of ozone to fall below 200 Dobson units, from the 250 recorded over central Siberia. It is predicted that the thinning layer would affect parts of Scandinavia and Eastern Europe on March 30–31.
On October 2, 2011, a study was published in the journal Nature, which said that between December 2010 and March 2011 up to 80 percent of the ozone in the atmosphere at about above the surface was destroyed. The level of ozone depletion was severe enough that scientists said it could be compared to the ozone hole that forms over Antarctica every winter. According to the study, "for the first time, sufficient loss occurred to reasonably be described as an Arctic ozone hole." The study analyzed data from the Aura and CALIPSO satellites, and determined that the larger-than-normal ozone loss was due to an unusually long period of cold weather in the Arctic, some 30 days more than typical, which allowed for more ozone-destroying chlorine compounds to be created. According to Lamont Poole, a co-author of the study, cloud and aerosol particles on which the chlorine compounds are found "were abundant in the Arctic until mid March 2011—much later than usual—with average amounts at some altitudes similar to those observed in the Antarctic, and dramatically larger than the near-zero values seen in March in most Arctic winters".
In 2013, researchers analyzed the data and found the 2010–2011 Arctic event did not reach the ozone depletion levels to classify as a true hole. A hole in the ozone is generally classified as 220 Dobson units or lower; the Arctic hole did not approach that low level. It has since been classified as a "mini-hole." | Ozone depletion | Wikipedia | 438 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
Following the ozone depletion in 1997 and 2011, a 90% drop in ozone was measured by weather balloons over the Arctic in March 2020, as they normally recorded 3.5 parts per million of ozone, compared to only around 0.3 parts per million lastly, due to the coldest temperatures ever recorded since 1979, and a strong polar vortex which allowed chemicals, including chlorine and bromine, to reduce ozone.
A rare hole, the result of unusually low temperatures in the atmosphere above the North Pole, was studied in 2020.
Tibet ozone hole
As winters that are colder are more affected, at times there is an ozone hole over Tibet. In 2006, a 2.5 million square kilometer ozone hole was detected over Tibet. Again in 2011, an ozone hole appeared over mountainous regions of Tibet, Xinjiang, Qinghai and the Hindu Kush, along with an unprecedented hole over the Arctic, though the Tibet one was far less intense than the ones over the Arctic or Antarctic.
Potential depletion by storm clouds
Research in 2012 showed that the same process that produces the ozone hole over Antarctica, occurs over summer storm clouds in the United States, and thus may be destroying ozone there as well.
Ozone hole over tropics
Physicist Qing-Bin Lu, of the University of Waterloo, claimed to have discovered a large, all-season ozone hole in the lower stratosphere over the tropics in July 2022. However, other researchers in the field refuted this claim, stating that the research was riddled with "serious errors and unsubstantiated assertions." According to Dr Paul Young, a lead author of the 2022 WMO/UNEP Scientific Assessment of Ozone Depletion, "The author's identification of a 'tropical ozone hole' is down to him looking at percentage changes in ozone, rather than absolute changes, with the latter being much more relevant for damaging UV reaching the surface." Specifically, Lu's work defines "ozone hole" as "an area with O3 loss in percent larger than 25%, with respect to the undisturbed O3 value when there were no significant CFCs in the stratosphere (~ in the 1960s)" instead of the general definition of 220 Dobson units or lower. Dr Marta Abalos Alvarez has added "Ozone depletion in the tropics is nothing new and is mainly due to the acceleration of the Brewer-Dobson circulation."
Depletion caused by wildfire smoke | Ozone depletion | Wikipedia | 501 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
Analyzing the atmospheric impacts of the 2019–2020 Australian bushfire season, scientists led by MIT researcher Susan Solomon found the smoke destroyed 3–5% of ozone in affected areas of the Southern Hemisphere. Smoke particles absorb hydrogen chloride and act as a catalyst to create chlorine radicals that destroy ozone.
Ozone depletion and global warming
Among others, Robert Watson had a role in the science assessment and in the regulation efforts of ozone depletion and global warming. Prior to the 1980s, the EU, NASA, NAS, UNEP, WMO and the British government had dissenting scientific reports and Watson played a role in the process of unified assessments. Based on the experience with the ozone case, the IPCC started to work on a unified reporting and science assessment to reach a consensus to provide the IPCC Summary for Policymakers.
There are various areas of linkage between ozone depletion and global warming science: | Ozone depletion | Wikipedia | 183 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
The same radiative forcing that produces global warming is expected to cool the stratosphere. This cooling, in turn, is expected to produce a relative increase in ozone () depletion in polar areas and the frequency of ozone holes.
Conversely, ozone depletion represents a radiative forcing of the climate system. There are two opposing effects: Reduced ozone causes the stratosphere to absorb less solar radiation, thus cooling the stratosphere while warming the troposphere; the resulting colder stratosphere emits less long-wave radiation downward, thus cooling the troposphere. Overall, the cooling dominates; the IPCC concludes "observed stratospheric losses over the past two decades have caused a negative forcing of the surface-troposphere system" of about −0.15 ± 0.10 watts per square meter (W/m2).
One of the strongest predictions of the greenhouse effect is that the stratosphere will cool. Although this cooling has been observed, it is not trivial to separate the effects of changes in the concentration of greenhouse gases and ozone depletion since both will lead to cooling. However, this can be done by numerical stratospheric modeling. Results from the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory show that above , the greenhouse gases dominate the cooling.
Ozone depleting chemicals are also often greenhouse gases. The increases in concentrations of these chemicals have produced 0.34 ± 0.03 W/m2 of radiative forcing, corresponding to about 14 percent of the total radiative forcing from increases in the concentrations of well-mixed greenhouse gases.
The long term modeling of the process, its measurement, study, design of theories and testing take decades to document, gain wide acceptance, and ultimately become the dominant paradigm. Several theories about the destruction of ozone were hypothesized in the 1980s, published in the late 1990s, and are now being investigated. Dr Drew Schindell, and Dr Paul Newman, NASA Goddard, proposed a theory in the late 1990s, using computational modeling methods to model ozone destruction, that accounted for 78 percent of the ozone destroyed. Further refinement of that model accounted for 89 percent of the ozone destroyed, but pushed back the estimated recovery of the ozone hole from 75 years to 150 years. (An important part of that model is the lack of stratospheric flight due to depletion of fossil fuels.) | Ozone depletion | Wikipedia | 495 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
In 2019, NASA reported that there was no significant relation between size of the ozone hole and climate change.
Misconceptions
CFC weight
Since CFC molecules are heavier than air (nitrogen or oxygen), it is commonly believed that the CFC molecules cannot reach the stratosphere in significant amounts. However, atmospheric gases are not sorted by weight at these altitudes; the forces of wind can fully mix the gases in the atmosphere. Some of the heavier CFCs are not evenly distributed.
Percentage of man-made chlorine
Another misconception is that "it is generally accepted that natural sources of tropospheric chlorine are four to five times larger than man-made ones." While this statement is strictly true, tropospheric chlorine is irrelevant; it is stratospheric chlorine that affects ozone depletion. Chlorine from ocean spray is soluble and thus is washed by rainfall before it reaches the stratosphere. CFCs, in contrast, are insoluble and long-lived, allowing them to reach the stratosphere. In the lower atmosphere, there is much more chlorine from CFCs and related haloalkanes than there is in HCl from salt spray, and in the stratosphere halocarbons are dominant. Only methyl chloride, which is one of these halocarbons, has a mainly natural source, and it is responsible for about 20 percent of the chlorine in the stratosphere; the remaining 80 percent comes from manmade sources.
Very violent volcanic eruptions can inject HCl into the stratosphere, but researchers have shown that the contribution is not significant compared to that from CFCs. A similar erroneous assertion is that soluble halogen compounds from the volcanic plume of Mount Erebus on Ross Island, Antarctica are a major contributor to the Antarctic ozone hole.
Nevertheless, a 2015 study showed that the role of Mount Erebus volcano in the Antarctic ozone depletion was probably underestimated. Based on the NCEP/NCAR reanalysis data over the last 35 years and by using the NOAA HYSPLIT trajectory model, researchers showed that Erebus volcano gas emissions (including hydrogen chloride (HCl)) can reach the Antarctic stratosphere via high-latitude cyclones and then the polar vortex. Depending on Erebus volcano activity, the additional annual HCl mass entering the stratosphere from Erebus varies from 1.0 to 14.3 kt. | Ozone depletion | Wikipedia | 511 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
First observation
G.M.B. Dobson mentioned that when springtime ozone levels in the Antarctic over Halley Bay were first measured in 1956, he was surprised to find that they were ~320 DU, or about 150 DU below spring Arctic levels of ~450 DU. These were at that time the only known Antarctic ozone values available. What Dobson describes is essentially the baseline from which the ozone hole is measured: actual ozone hole values are in the 150–100 DU range.
The discrepancy between the Arctic and Antarctic noted by Dobson was primarily a matter of timing: during the Arctic spring, ozone levels rose smoothly, peaking in April, whereas in the Antarctic they stayed approximately constant during early spring, rising abruptly in November when the polar vortex broke down.
The behavior seen in the Antarctic ozone hole is different. Instead of staying constant, early springtime ozone levels drop from their already low winter values, by as much as 50 percent, and normal values are not reached again until December.
Location of hole
Some people thought that the ozone hole should be above the sources of CFCs. However, CFCs are well mixed globally in the troposphere and stratosphere. The reason for occurrence of the ozone hole above Antarctica is not because there are more CFCs concentrated but because the low temperatures help form polar stratospheric clouds. In fact, there are findings of significant and localized "ozone holes" above other parts of the Earth, such as above Central Asia.
Awareness campaigns
Public misconceptions and misunderstandings of complex issues like ozone depletion are common. The limited scientific knowledge of the public led to confusion about global warming or the perception of global warming as a subset of the "ozone hole". In the beginning, classical green NGOs refrained from using CFC depletion for campaigning, as they assumed the topic was too complicated. They became active much later, e.g. in Greenpeace's support for a CFC-free refrigerator produced by the former East German company VEB dkk Scharfenstein. | Ozone depletion | Wikipedia | 414 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
The metaphors used in the CFC discussion (ozone shield, ozone hole) are not "exact" in the scientific sense. The "ozone hole" is more of a depression, less "a hole in the windshield". The ozone does not disappear through the layer, nor is there a uniform "thinning" of the ozone layer. However, they resonated better with non-scientists and their concerns. The ozone hole was seen as a "hot issue" and imminent risk as laypeople feared severe personal consequences such as skin cancer, cataracts, damage to plants, and reduction of plankton populations in the ocean's photic zone. Not only on the policy level, ozone regulation compared to climate change fared much better in public opinion. Americans voluntarily switched away from aerosol sprays before legislation was enforced, while climate change failed to achieve comparable concern and public action. The sudden identification in 1985 that there was a substantial "hole" was widely reported in the press. The especially rapid ozone depletion in Antarctica had previously been dismissed as a measurement error. Scientific consensus was established after regulation.
While the Antarctic ozone hole has a relatively small effect on global ozone, the hole has generated a great deal of public interest because:
Many have worried that ozone holes might start appearing over other areas of the globe, though to date the only other large-scale depletion is a smaller ozone "dimple" observed during the Arctic spring around the North Pole. Ozone at middle latitudes has declined, but by a much smaller extent (a decrease of about 4–5 percent).
If stratospheric conditions become more severe (cooler temperatures, more clouds, more active chlorine), global ozone may decrease at a greater pace. Standard global warming theory predicts that the stratosphere will cool.
When the Antarctic ozone hole breaks up each year, the ozone-depleted air drifts into nearby regions. Decreases in the ozone level of up to 10 percent have been reported in New Zealand in the month following the breakup of the Antarctic ozone hole, with ultraviolet-B radiation intensities increasing by more than 15 percent since the 1970s.
World Ozone Day
In 1994, the United Nations General Assembly voted to designate September 16 as the International Day for the Preservation of the Ozone Layer, or "World Ozone Day". The designation commemorates the signing of the Montreal Protocol on that date in 1987. | Ozone depletion | Wikipedia | 487 | 44183 | https://en.wikipedia.org/wiki/Ozone%20depletion | Physical sciences | Atmosphere | null |
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g., kaolin, Al2Si2O5(OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. Shale is characterized by its tendency to split into thin layers (laminae) less than one centimeter in thickness. This property is called fissility. Shale is the most common sedimentary rock.
The term shale is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the narrower sense of clay-rich fissile mudrock.
Texture
Shale typically exhibits varying degrees of fissility. Because of the parallel orientation of clay mineral flakes in shale, it breaks into thin layers, often splintery and usually parallel to the otherwise indistinguishable bedding planes. Non-fissile rocks of similar composition and particle size (less than 0.0625 mm) are described as mudstones (1/3 to 2/3 silt particles) or claystones (less than 1/3 silt). Rocks with similar particle sizes but with less clay (greater than 2/3 silt) and therefore grittier are siltstones.
Composition and color
Shales are typically gray in color and are composed of clay minerals and quartz grains. The addition of variable amounts of minor constituents alters the color of the rock. Red, brown and green colors are indicative of ferric oxide (hematite – reds), iron hydroxide (goethite – browns and limonite – yellow), or micaceous minerals (chlorite, biotite and illite – greens). The color shifts from reddish to greenish as iron in the oxidized (ferric) state is converted to iron in the reduced (ferrous) state. Black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment. Pale blue to blue-green shales typically are rich in carbonate minerals. | Shale | Wikipedia | 435 | 44211 | https://en.wikipedia.org/wiki/Shale | Physical sciences | Sedimentary rocks | Earth science |
Clays are the major constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite. Clay minerals of Late Tertiary mudstones are expandable smectites, whereas in older rocks (especially in mid-to early Paleozoic shales) illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron and water. These released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite and albite, all trace to minor (except quartz) minerals found in shales and other mudrocks. A typical shale is composed of about 58% clay minerals, 28% quartz, 6% feldspar, 5% carbonate minerals, and 2% iron oxides. Most of the quartz is detrital (part of the original sediments that formed the shale) rather than authigenic (crystallized within the shale after deposition).
Shales and other mudrocks contain roughly 95 percent of the organic matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale. Black shales, which form in anoxic conditions, contain reduced free carbon along with ferrous iron (Fe2+) and sulfur (S2−). Amorphous iron sulfide, along with carbon, produce the black coloration. Because amorphous iron sulfide gradually converts to pyrite, which is not an important pigment, young shales may be quite dark from their iron sulfide content, in spite of a modest carbon content (less than 1%), while a black color in an ancient shale indicates a high carbon content.
Most shales are marine in origin, and the groundwater in shale formations is often highly saline. There is evidence that shale acts as a semipermeable medium, allowing water to pass through while retaining dissolved salts. | Shale | Wikipedia | 404 | 44211 | https://en.wikipedia.org/wiki/Shale | Physical sciences | Sedimentary rocks | Earth science |
Formation
The fine particles that compose shale can remain suspended in water long after the larger particles of sand have been deposited. As a result, shales are typically deposited in very slow moving water and are often found in lakes and lagoonal deposits, in river deltas, on floodplains and offshore below the wave base. Thick deposits of shale are found near ancient continental margins and foreland basins. Some of the most widespread shale formations were deposited by epicontinental seas. Black shales are common in Cretaceous strata on the margins of the Atlantic Ocean, where they were deposited in fault-bounded silled basins associated with the opening of the Atlantic during the breakup of Pangaea. These basins were anoxic, in part because of restricted circulation in the narrow Atlantic, and in part because the very warm Cretaceous seas lacked the circulation of cold bottom water that oxygenates the deep oceans today.
Most clay must be deposited as aggregates and floccules, since the settling rate of individual clay particles is extremely slow. Flocculation is very rapid once the clay encounters highly saline sea water. Whereas individual clay particles are less than 4 microns in size, the clumps of clay particles produced by flocculation vary in size from a few tens of microns to over 700 microns in diameter. The floccules start out water-rich, but much of the water is expelled from the floccules as the clay minerals bind more tightly together over time (a process called syneresis). Clay pelletization by organisms that filter feed is important where flocculation is inhibited. Filter feeders produce an estimated 12 metric tons of clay pellets per square kilometer per year along the U.S. Gulf Coast.
As sediments continue to accumulate, the older, more deeply buried sediments begin to undergo diagenesis. This mostly consists of compaction and lithification of the clay and silt particles. Early stages of diagenesis, described as eogenesis, take place at shallow depths (a few tens of meters) and are characterized by bioturbation and mineralogical changes in the sediments, with only slight compaction. Pyrite may be formed in anoxic mud at this stage of diagenesis. | Shale | Wikipedia | 455 | 44211 | https://en.wikipedia.org/wiki/Shale | Physical sciences | Sedimentary rocks | Earth science |
Deeper burial is accompanied by mesogenesis, during which most of the compaction and lithification takes place. As the sediments come under increasing pressure from overlying sediments, sediment grains move into more compact arrangements, ductile grains (such as clay mineral grains) are deformed, and pore space is reduced. In addition to this physical compaction, chemical compaction may take place via pressure solution. Points of contact between grains are under the greatest strain, and the strained mineral is more soluble than the rest of the grain. As a result, the contact points are dissolved away, allowing the grains to come into closer contact.
It is during compaction that shale develops its fissility, likely through mechanical compaction of the original open framework of clay particles. The particles become strongly oriented into parallel layers that give the shale its distinctive fabric. Fissility likely develops early in the compaction process, at relatively shallow depth, since fissility does not seem to vary with depth in thick formations. Kaolinite flakes have less tendency to align in parallel layers than other clays, so kaolinite-rich clay is more likely to form nonfissile mudstone than shale. On the other hand, black shales often have very pronounced fissility (paper shales) due to binding of hydrocarbon molecules to the faces of the clay particles, which weakens the binding between particles.
Lithification follows closely on compaction, as increased temperatures at depth hasten deposition of cement that binds the grains together. Pressure solution contributes to cementing, as the mineral dissolved from strained contact points is redeposited in the unstrained pore spaces. The clay minerals may be altered as well. For example, smectite is altered to illite at temperatures of about , releasing water in the process. Other alteration reactions include the alteration of smectite to chlorite and of kaolinite to illite at temperatures between . Because of these reactions, illite composes 80% of Precambrian shales, versus about 25% of young shales.
Unroofing of buried shale is accompanied by telogenesis, the third and final stage of diagenesis. As erosion reduces the depth of burial, renewed exposure to meteoric water produces additional changes to the shale, such as dissolution of some of the cement to produce secondary porosity. Pyrite may be oxidized to produce gypsum. | Shale | Wikipedia | 496 | 44211 | https://en.wikipedia.org/wiki/Shale | Physical sciences | Sedimentary rocks | Earth science |
Black shales are dark, as a result of being especially rich in unoxidized carbon. Common in some Paleozoic and Mesozoic strata, black shales were deposited in anoxic, reducing environments, such as in stagnant water columns. Some black shales contain abundant heavy metals such as molybdenum, uranium, vanadium, and zinc. The enriched values are of controversial origin, having been alternatively attributed to input from hydrothermal fluids during or after sedimentation or to slow accumulation from sea water over long periods of sedimentation.
Fossils, animal tracks or burrows and even raindrop impressions are sometimes preserved on shale bedding surfaces. Shales may also contain concretions consisting of pyrite, apatite, or various carbonate minerals.
Shales that are subject to heat and pressure of metamorphism alter into a hard, fissile, metamorphic rock known as slate. With continued increase in metamorphic grade the sequence is phyllite, then schist and finally gneiss.
As hydrocarbon source rock
Shale is the most common source rock for hydrocarbons (natural gas and petroleum). The lack of coarse sediments in most shale beds reflects the absence of strong currents in the waters of the depositional basin. These might have oxygenated the waters and destroyed organic matter before it could accumulate. The absence of carbonate rock in shale beds reflects the absence of organisms that might have secreted carbonate skeletons, also likely due to an anoxic environment. As a result, about 95% of organic matter in sedimentary rocks is found in shales and other mudrocks. Individual shale beds typically have an organic matter content of about 1%, but the richest source rocks may contain as much as 40% organic matter.
The organic matter in shale is converted over time from the original proteins, polysaccharides, lipids, and other organic molecules to kerogen, which at the higher temperatures found at greater depths of burial is further converted to graphite and petroleum.
Historical mining terminology
Before the mid-19th century, the terms slate, shale and schist were not sharply distinguished. In the context of underground coal mining, shale was frequently referred to as slate well into the 20th century. Black shale associated with coal seams is called black metal. | Shale | Wikipedia | 467 | 44211 | https://en.wikipedia.org/wiki/Shale | Physical sciences | Sedimentary rocks | Earth science |
Slate is a fine-grained, foliated, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade, regional metamorphism. It is the finest-grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.
The foliation in slate, called "slaty cleavage", is caused by strong compression in which fine-grained clay forms flakes to regrow in planes perpendicular to the compression. When expertly "cut" by striking parallel to the foliation with a specialized tool in the quarry, many slates display a property called fissility, forming smooth, flat sheets of stone which have long been used for roofing, floor tiles, and other purposes. Slate is frequently grey in color, especially when seen en masse covering roofs. However, slate occurs in a variety of colors even from a single locality; for example, slate from North Wales can be found in many shades of grey, from pale to dark, and may also be purple, green, or cyan. Slate is not to be confused with shale, from which it may be formed, or schist.
The word "slate" is also used for certain types of object made from slate rock. It may mean a single roofing tile made of slate, or a writing slate, which was traditionally a small, smooth piece of the rock, often framed in wood, used with chalk as a notepad or notice board, and especially for recording charges in pubs and inns. The phrases "clean slate" and "blank slate" come from this usage.
Description
Slate is a fine-grained, metamorphic rock that shows no obvious compositional layering but can easily be split into thin slabs and plates. It is usually formed by low-grade regional metamorphism of mudrock. This mild degree of metamorphism produces a rock in which the individual mineral crystals remain microscopic in size, producing a characteristic slaty cleavage in which fresh cleavage surfaces appear dull. This is in contrast to the silky cleaved surfaces of phyllite, which is the next-higher grade of metamorphic rock derived from mudstone. The direction of cleavage is independent of any sedimentary structures in the original mudrock, reflecting instead the direction of regional compression. | Slate | Wikipedia | 490 | 44214 | https://en.wikipedia.org/wiki/Slate | Physical sciences | Petrology | null |
Slaty cleavage is continuous, meaning that the individual cleavage planes are too closely spaced to be discernible in hand samples. The texture of the slate is totally dominated by these pervasive cleavage planes. Under a microscope, the slate is found to consist of very thin lenses of quartz and feldspar (QF-domains) separated by layers of mica (M-domains). These are typically less than 100 μm (micron) thick. Because slate was formed in low heat and pressure, compared to most other metamorphic rocks, some fossils can be found in slate; sometimes even microscopic remains of delicate organisms can be found in slate.
The process of conversion of mudrock to slate involves a loss of up to 50% of the volume of the mudrock as it is compacted. Grains of platy minerals, such as clay minerals, are rotated to form parallel layers perpendicular to the direction of compaction, which begin to impart cleavage to the rock. Slaty cleavage is fully developed as the clay minerals begin to be converted to chlorite and mica. Organic carbon in the rock is converted to graphite.
Slate is mainly composed of the minerals quartz, illite, and chlorite, which account for up to 95% of its composition. The most important accessory minerals are iron oxides (such as hematite and magnetite), iron sulfides (such as pyrite), and carbonate minerals. Feldspar may be present as albite or, less commonly, orthoclase. Occasionally, as in the purple slates of North Wales, ferrous (iron(II)) reduction spheres form around iron nuclei, leaving a light-green, spotted texture. These spheres are sometimes deformed by a subsequent applied stress field into ovoids, which appear as ellipses when viewed on a cleavage plane of the specimen. However, some evidence shows that reduced spots may also form after deformation and acquire an elliptical shape from preferential infiltration along the cleavage direction, so caution is required in using reduction ellipsoids to estimate deformation. | Slate | Wikipedia | 431 | 44214 | https://en.wikipedia.org/wiki/Slate | Physical sciences | Petrology | null |
Terminology
Before the mid-19th century, the terms "slate", "shale", and "schist" were not sharply distinguished. In the context of underground coal mining in the United States, the term slate was commonly used to refer to shale well into the 20th century. For example, roof slate referred to shale above a coal seam, and draw slate referred to shale that fell from the mine roof as the coal was removed.
The British Geological Survey recommends that the term "slate" be used in scientific writings only when very little else is known about the rock that would allow a more definite classification. For example, if the characteristics of the rock show definitely that it was formed by metamorphosis of shale, it should be described in scientific writings as a metashale. If its origin is uncertain, but the rock is known to be rich in mica, it should be described as a pelite.
Uses
Construction
Slate can be made into roofing slate, a type of roof tile which are installed by a slater. Slate has two lines of breakability—cleavage and grain—which make it possible to split the stone into thin sheets. When broken, slate retains a natural appearance while remaining relatively flat and easy to stack. A series of "slate booms" occurred in Europe from the 1870s until the First World War following improvements in railway, road and waterway transportation systems.
Slate is particularly suitable as a roofing material as it has an extremely low water absorption index of less than 0.4%, making the material resistant to frost damage. Natural slate, which requires only minimal processing, has an embodied energy that compares favorably with other roofing materials.
Natural slate is used by building professionals as a result of its beauty and durability. Slate is incredibly durable and can last several hundred years, often with little or no maintenance. Natural slate is also fire resistant and energy efficient.
Slate roof tiles are usually fixed (fastened) either with nails or with hooks (as is common with Spanish slate). In the UK, fixing is typically with double nails onto timber battens (England and Wales) or nailed directly onto timber sarking boards (Scotland and Northern Ireland). Nails were traditionally of copper, although there are modern alloy and stainless steel alternatives. Both these methods, if used properly, provide a long-lasting weathertight roof with a lifespan of around 60–125 years. | Slate | Wikipedia | 481 | 44214 | https://en.wikipedia.org/wiki/Slate | Physical sciences | Petrology | null |
Some mainland European slate suppliers suggest that using hook fixing means that:
Areas of weakness on the tile are fewer since no holes have to be drilled
Roofing features such as valleys and domes are easier to create since narrow tiles can be used
Hook fixing is particularly suitable in regions subject to severe weather conditions, since there is greater resistance to wind uplift, as the lower edge of the slate is secured.
The metal hooks are, however, visible and may be unsuitable for historic properties.
Slate tiles are often used for interior and exterior flooring, stairs, walkways and wall cladding. Tiles are installed and set on mortar and grouted along the edges. Chemical sealants are often used on tiles to improve durability and appearance, increase stain resistance, reduce efflorescence, and increase or reduce surface smoothness. Tiles are often sold gauged, meaning that the back surface is ground for ease of installation. Slate flooring can be slippery when used in external locations subject to rain.
Slate tiles were used in 19th century UK building construction (apart from roofs) and in slate quarrying areas such as Blaenau Ffestiniog and Bethesda, Wales there are still many buildings wholly constructed of slate. Slates can also be set into walls to provide a rudimentary damp-proof membrane. Small offcuts are used as shims to level floor joists. In areas where slate is plentiful it is also used in pieces of various sizes for building walls and hedges, sometimes combined with other kinds of stone.
Other uses
Because it is a good electrical insulator and fireproof, it was used to construct early-20th-century electric switchboards and relay controls for large electric motors. Because of its thermal stability and chemical inertness, slate has been used for laboratory bench tops and for billiard table tops.
Slate was used by earlier cultures as whetstone to hone knives, but whetstones are nowadays more typically made of quartz. In 18th- and 19th-century schools, slate was extensively used for blackboards and individual writing slates, for which slate or chalk pencils were used. In modern homes slate is often used as table coasters.
In areas where it is available, high-quality slate is used for tombstones and commemorative tablets. In some cases slate was used by the ancient Maya civilization to fashion stelae. Slate was the traditional material of choice for black Go stones in Japan, alongside clamshell for white stones. It is now considered to be a luxury. | Slate | Wikipedia | 512 | 44214 | https://en.wikipedia.org/wiki/Slate | Physical sciences | Petrology | null |
Pennsylvania slate is widely used in the manufacture of turkey calls used for hunting turkeys. The tones produced from the slate, when scratched with various species of wood striker, imitates almost exactly the calls of all four species of wild turkey in North America: eastern, Rio Grande, Osceola and Merriam's.
Extraction
Slate is found in the Arctic and was used by Inuit to make the blades for ulus. China has vast slate deposits; in recent years its export of finished and unfinished slate has increased. Deposits of slate exist throughout Australia, with large reserves quarried in the Adelaide Hills in Willunga, Kanmantoo, and the Mid North at Mintaro and Spalding. Slate is abundant in Brazil, the world's second-largest producer of slate, around Papagaios in Minas Gerais, which extracts 95 percent of Brazil's slate. However, not all "slate" products from Brazil are entitled to bear the CE mark.
Most slate in Europe today comes from Spain, the world's largest producer and exporter of natural slate, and 90 percent of Europe's natural slate used for roofing originates from the slate industry there. Lesser slate-producing regions in present-day Europe include Wales (with UNESCO landscape status and a museum at Llanberis), Cornwall (famously the village of Delabole), Cumbria (see Burlington Slate Quarries, Honister Slate Mine and Skiddaw Slate) and, formerly in the West Highlands of Scotland, around Ballachulish and the Slate Islands in the United Kingdom. Parts of France (Anjou, Loire Valley, Ardennes, Brittany, Savoie) and Belgium (Ardennes), Liguria in northern Italy, especially between the town of Lavagna (whose name is inherited as the term for chalkboard in Italian) and Fontanabuona valley; Portugal especially around Valongo in the north of the country. Germany's Moselle River region, Hunsrück (with a former mine open as a museum at Fell), Eifel, Westerwald, Thuringia and north Bavaria; and Alta, Norway (actually schist, not a true slate). Some of the slate from Wales and Cumbria is colored slate (non-blue): purple and formerly green in Wales and green in Cumbria. | Slate | Wikipedia | 472 | 44214 | https://en.wikipedia.org/wiki/Slate | Physical sciences | Petrology | null |
In North America, slate is produced in Newfoundland, eastern Pennsylvania, Buckingham County, Virginia, and the Slate Valley region in Vermont and New York, where colored slate is mined in the Granville, New York, area. A major slating operation existed in Monson, Maine, during the late 19th and early 20th centuries, where the slate is usually dark purple to blackish, and many local structures are roofed with slate tiles. The roof of St. Patrick's Cathedral in New York City and the headstone of John F. Kennedy's gravesite in Arlington National Cemetery are both made of Monson slate. | Slate | Wikipedia | 122 | 44214 | https://en.wikipedia.org/wiki/Slate | Physical sciences | Petrology | null |
Menhaden, also known as mossbunker, bunker, and "the most important fish in the sea", are forage fish of the genera Brevoortia and Ethmidium, two genera of marine fish in the order Clupeiformes. Menhaden is a blend of poghaden (pogy for short) and an Algonquian word akin to Narragansett munnawhatteaûg, derived from munnohquohteau ("he fertilizes"), referring to their use of the fish as fertilizer. It is generally thought that Pilgrims were advised by Tisquantum (also known as Squanto) to plant menhaden with their crops.
Description
Menhaden are flat and have soft flesh and a deeply forked tail. They rarely exceed in length, and have a varied weight range. Gulf menhaden and Atlantic menhaden are small oily-fleshed fish, bright silver, and characterized by a series of smaller spots behind the main humeral spot. They tend to have larger scales than yellowfin menhaden and finescale menhaden. In addition, yellowfin menhaden tail rays are a bright yellow in contrast to those of the Atlantic menhaden.
Taxonomy
Recent taxonomic work using DNA comparisons have organized the North American menhadens into large-scaled (Gulf and Atlantic menhaden) and small-scaled (Finescale and Yellowfin menhaden) designations.
The menhaden consist of two genera and seven species:
Genus Brevoortia T. N. Gill, 1861
Brevoortia aurea (Spix & Agassiz, 1829) (Brazilian menhaden)
Brevoortia gunteri Hildebrand, 1948 (Finescale menhaden)
Brevoortia patronus Goode, 1878 (Gulf menhaden)
Brevoortia pectinata (Jenyns, 1842) (Argentine menhaden)
Brevoortia smithi Hildebrand, 1941 (Yellowfin menhaden)
Brevoortia tyrannus (Latrobe, 1802) (Atlantic menhaden)
Genus Ethmidium W. F. Thompson, 1916
Ethmidium maculatum (Valenciennes, 1847) (Pacific menhaden) | Menhaden | Wikipedia | 479 | 44217 | https://en.wikipedia.org/wiki/Menhaden | Biology and health sciences | Clupeiformes | Animals |
Distribution
Finescale menhaden range from the Yucatán to Louisiana.
Yellowfin menhaden range from Louisiana to Virginia.
Gulf menhaden range from the Yucatán Peninsula, Mexico, to Tampa Bay, Florida.
Atlantic menhaden range from Jupiter Inlet, Florida, to Nova Scotia; Atlantic menhaden seasonally migrate along the coast; in June, mature adults typically are in the northern portion of the coastline with sub-adults and juveniles located in the southern portion.
The various species of menhaden occur anywhere from estuarine waters outward to the continental shelf; menhaden grow in less saline waters of estuaries and may be found in bays and lagoons, as well as at river mouths; adults appear to prefer water temperatures near 18 °C.
Ecology
Menhaden are filter feeders that travel in large, slow-moving, and tightly packed schools with open mouths. Filter feeders typically take into their open mouths "materials in the same proportions as they occur in ambient waters". Menhaden have two main sources of food: phytoplankton and zooplankton. A menhaden's diet varies considerably over the course of its lifetime, and is directly related to its size. The smallest menhaden, typically those under one year old, eat primarily phytoplankton. After that age, adult menhaden gradually shift to a diet comprised almost exclusively of zooplankton.
Menhaden are omnivorous filter feeders, feeding by straining plankton and algae from water. Along with oysters, which filter water on the seabed, menhaden play a key role in the food chain in estuaries and bays. Atlantic menhaden are an important link between plankton and upper level predators. Because of their filter feeding abilities, "menhaden consume and redistribute a significant amount of energy within and between Chesapeake Bay and other estuaries, and the coastal ocean." Because they play this role, and their abundance, menhaden are an invaluable prey species for many predatory fish, such as striped bass, bluefish, mackerel, flounder, tuna, drums, and sharks. They are also a very important food source for many birds, including egrets, ospreys, seagulls, northern gannets, pelicans, and herons. | Menhaden | Wikipedia | 484 | 44217 | https://en.wikipedia.org/wiki/Menhaden | Biology and health sciences | Clupeiformes | Animals |
In 2012, the Atlantic States Marine Fisheries Commission declared that the Atlantic menhaden was depleted due to overfishing. The decision was driven by issues with water quality in the Chesapeake Bay and failing efforts to re-introduce predator species, due to lack of menhaden on which they could feed.
Menhaden are crucial not only because of their keystone species-status in the food web, but also because of their ecological services. The way menhaden filter feed on phytoplankton helps to mitigate toxic algal blooms. These algal blooms, which are often detrimental to a number of fish, bird, and marine mammal species, create hypoxic conditions. The phytoplankton being preyed upon are photosynthetic organisms, converting sunlight into energy which is then transferred to menhaden and then to bigger species of fish or other larger marine organisms such as birds or mammals. The consequence of this behavior is that if menhaden are eliminated or significantly decreased, there are limited means of energy transfer among trophic levels – making menhaden a true keystone species with ecological services that are invaluable to humans.
Habitat
Menhaden are a pelagic schooling fish that migrate inshore during the summer and off-shore in the winter months. The juvenile and larval menhaden migrate to shore and inland waterways through currents during summer months to grow while feeding on the phytoplankton and eventually zooplankton once they have matured. Commercially caught menhaden have been recorded in waters of around 5 to 24 ‰, as well as in hypersaline waters around 60 ‰.
Reproduction
Menhaden reproduce in open oceans externally, however, the female does not carry eggs with them during the process as they are released into the water column at the planktonic level as gametes and sperm. Currently, functional hermaphroditism is unknown to the species and identification of sex of the individual organism cannot be determined externally due to the lack of accessory reproductive organs. These fish breed during the winter months through December to March and the eggs and juveniles navigate towards estuaries and inland waterways through tides and currents.
Human use
Menhaden are not used directly for food. They are processed into fish oil and fish meal that are used as food ingredients, animal feed, and dietary supplements. The flesh has a high omega-3 fat content. Fish oil made from menhaden also is used as a raw material for products such as lipstick. | Menhaden | Wikipedia | 508 | 44217 | https://en.wikipedia.org/wiki/Menhaden | Biology and health sciences | Clupeiformes | Animals |
Fisheries
According to the Virginia Institute of Marine Science (VIMS), there are two established commercial fisheries for menhaden. The first is known as a reduction fishery. The second is known as a bait fishery, which harvests menhaden for the use of both commercial and recreational fishermen. Commercial fishermen, especially crabbers in the Chesapeake Bay area, use menhaden to bait their traps or hooks. The recreational fisherman use ground menhaden chum as a fish attractant, and whole fish as bait. The total harvest is approximately 500 million fish per year. Atlantic menhaden are harvested using purse seines.
Omega Protein – a reduction fishery company with operations in the northwest Atlantic and the Gulf of Mexico – takes 90% of the total menhaden harvest in the United States. In October 2005, the Atlantic States Marine Fisheries Commission (ASMFC) approved an addendum to Amendment 1 of the Interstate Fishery Management Plan for Atlantic Menhaden, which "established a five-year annual cap on reduction fishery landings in the Chesapeake Bay", imposing a limit on reduction fishery operations for 2006–2010. In November 2006, that cap was established at 109,020 metric tons; this cap remained in place until 2013.
In December 2012, in the face of the depletion of Atlantic menhaden, the ASMFC implemented another cap, effective in 2013 and 2014, for the Chesapeake Bay, this time at 87,216 metric tons, as well as a total allowable catch (TAC) of the species of 170,800 metric tons, a 20% reduction from the 2009–2011 average. The TAC was subsequently raised for 2015 and 2016 to 187,880 metric tons. The cap in the Chesapeake Bay was further lowered in November 2017 to 51,000 metric tons, but this came alongside a higher TAC of 216,000 metric tons. Omega Protein has been openly critical of these caps.
Uses for menhaden oil
Despite not being a popular fish for consumption, menhaden oil has many uses not only for humans but also for other animals. One element of menhaden oil is that it is high in omega-3 fatty acids. This molecule helps with lowering blood pressure, fixing abnormal heartbeats, reducing the chance of a heart attack or stroke, and other health benefits. It is due to this that menhaden oil can be used in supplements to help with the previously mentioned issues. | Menhaden | Wikipedia | 492 | 44217 | https://en.wikipedia.org/wiki/Menhaden | Biology and health sciences | Clupeiformes | Animals |
One way that menhaden oil benefits animals is seen in chickens. When menhaden oil was given to chickens in their feed, they had a lower chance of fatty liver disease. This was because of menhaden oil's high omega-3 fatty acid content, which took the place of omega-6 fatty acid, which is not as beneficial to animals. Another animal that benefits from omega-3 in menhaden oil is guinea pigs. When given menhaden oil in feed guinea pigs were shown to have a longer life span.
Risks of overfishing
According to the Chesapeake Bay Foundation, menhaden are the most important fish in the Bay. This is because they are a food source for many commercial important species like striped bass. They also manage the algal bloom occurrences in the Bay because they eat phytoplankton. Decreases in menhaden populations could also leave striped bass vulnerable to disease. In the past 20 years, the number of juvenile menhaden produced in the Chesapeake Bay have been decreasing (Refer to Atlantic Menhaden Graph on bay-wide mean catch per haul).
This is believed to be due to the overfishing of menhaden for their fish oil. This could seriously disrupt the food chain. In response, the Atlantic States Marine Fisheries Commission (ASMFC) put a cap on the Atlantic menhaden harvest in October 2020. This 10% cut to the harvest is the first to ever be seen for menhaden coast-wide. It also was the first vote to consider benchmarks known as "ecological reference points". This allows managers to account for a species role in the food chain when setting catch limits. This is different from the "single-species stock assessments" that were previously used which only accounted for the demand from the fishing industry rather than the demand from the food web. This cut to the harvest established a quota of 194,400 metric tons of menhaden for the 2021–2022 fishing season. It is the hope that this cut will allow menhaden to fulfill their role in the ecosystem while keeping the commercial fishery alive. | Menhaden | Wikipedia | 428 | 44217 | https://en.wikipedia.org/wiki/Menhaden | Biology and health sciences | Clupeiformes | Animals |
Cultural significance
After menhaden had been identified as a valuable alternative to whale oil in the 1870s, the menhaden fishery on the Chesapeake was worked by predominantly African-American crews on open boats hauling purse seines. The men employed sea chanties to help synchronize the hauling of the nets. These chanties pulled from West African, blues, and gospel sources and created a uniquely African American culture of chanty singing. By the late 1950s, hydraulic winches replaced the large crews of manual haulers, and the menhaden chanty tradition declined. | Menhaden | Wikipedia | 114 | 44217 | https://en.wikipedia.org/wiki/Menhaden | Biology and health sciences | Clupeiformes | Animals |
Non-coding DNA (ncDNA) sequences are components of an organism's DNA that do not encode protein sequences. Some non-coding DNA is transcribed into functional non-coding RNA molecules (e.g. transfer RNA, microRNA, piRNA, ribosomal RNA, and regulatory RNAs). Other functional regions of the non-coding DNA fraction include regulatory sequences that control gene expression; scaffold attachment regions; origins of DNA replication; centromeres; and telomeres. Some non-coding regions appear to be mostly nonfunctional, such as introns, pseudogenes, intergenic DNA, and fragments of transposons and viruses. Regions that are completely nonfunctional are called junk DNA.
Fraction of non-coding genomic DNA
In bacteria, the coding regions typically take up 88% of the genome. The remaining 12% does not encode proteins, but much of it still has biological function through genes where the RNA transcript is functional (non-coding genes) and regulatory sequences, which means that almost all of the bacterial genome has a function. The amount of coding DNA in eukaryotes is usually a much smaller fraction of the genome because eukaryotic genomes contain large amounts of repetitive DNA not found in prokaryotes. The human genome contains somewhere between 1–2% coding DNA. The exact number is not known because there are disputes over the number of functional coding exons and over the total size of the human genome. This means that 98–99% of the human genome consists of non-coding DNA and this includes many functional elements such as non-coding genes and regulatory sequences.
Genome size in eukaryotes can vary over a wide range, even between closely related species. This puzzling observation was originally known as the C-value Paradox where "C" refers to the haploid genome size. The paradox was resolved with the discovery that most of the differences were due to the expansion and contraction of repetitive DNA and not the number of genes. Some researchers speculated that this repetitive DNA was mostly junk DNA. The reasons for the changes in genome size are still being worked out and this problem is called the C-value Enigma. | Non-coding DNA | Wikipedia | 447 | 44284 | https://en.wikipedia.org/wiki/Non-coding%20DNA | Biology and health sciences | Molecular biology | Biology |
This led to the observation that the number of genes does not seem to correlate with perceived notions of complexity because the number of genes seems to be relatively constant, an issue termed the G-value Paradox. For example, the genome of the unicellular Polychaos dubium (formerly known as Amoeba dubia) has been reported to contain more than 200 times the amount of DNA in humans (i.e. more than 600 billion pairs of bases vs a bit more than 3 billion in humans). The pufferfish Takifugu rubripes genome is only about one eighth the size of the human genome, yet seems to have a comparable number of genes. Genes take up about 30% of the pufferfish genome and the coding DNA is about 10%. (Non-coding DNA = 90%.) The reduced size of the pufferfish genome is due to a reduction in the length of introns and less repetitive DNA.
Utricularia gibba, a bladderwort plant, has a very small nuclear genome (100.7 Mb) compared to most plants. It likely evolved from an ancestral genome that was 1,500 Mb in size. The bladderwort genome has roughly the same number of genes as other plants but the total amount of coding DNA comes to about 30% of the genome.
The remainder of the genome (70% non-coding DNA) consists of promoters and regulatory sequences that are shorter than those in other plant species. The genes contain introns but there are fewer of them and they are smaller than the introns in other plant genomes. There are noncoding genes, including many copies of ribosomal RNA genes. The genome also contains telomere sequences and centromeres as expected. Much of the repetitive DNA seen in other eukaryotes has been deleted from the bladderwort genome since that lineage split from those of other plants. About 59% of the bladderwort genome consists of transposon-related sequences but since the genome is so much smaller than other genomes, this represents a considerable reduction in the amount of this DNA. The authors of the original 2013 article note that claims of additional functional elements in the non-coding DNA of animals do not seem to apply to plant genomes. | Non-coding DNA | Wikipedia | 463 | 44284 | https://en.wikipedia.org/wiki/Non-coding%20DNA | Biology and health sciences | Molecular biology | Biology |
According to a New York Times article, during the evolution of this species, "... genetic junk that didn't serve a purpose was expunged, and the necessary stuff was kept." According to Victor Albert of the University of Buffalo, the plant is able to expunge its so-called junk DNA and "have a perfectly good multicellular plant with lots of different cells, organs, tissue types and flowers, and you can do it without the junk. Junk is not needed."
Types of non-coding DNA sequences
Noncoding genes
There are two types of genes: protein coding genes and noncoding genes. Noncoding genes are an important part of non-coding DNA and they include genes for transfer RNA and ribosomal RNA. These genes were discovered in the 1960s. Prokaryotic genomes contain genes for a number of other noncoding RNAs but noncoding RNA genes are much more common in eukaryotes.
Typical classes of noncoding genes in eukaryotes include genes for small nuclear RNAs (snRNAs), small nucleolar RNAs (sno RNAs), microRNAs (miRNAs), short interfering RNAs (siRNAs), PIWI-interacting RNAs (piRNAs), and long noncoding RNAs (lncRNAs). In addition, there are a number of unique RNA genes that produce catalytic RNAs.
Noncoding genes account for only a few percent of prokaryotic genomes but they can represent a vastly higher fraction in eukaryotic genomes. In humans, the noncoding genes take up at least 6% of the genome, largely because there are hundreds of copies of ribosomal RNA genes. Protein-coding genes occupy about 38% of the genome; a fraction that is much higher than the coding region because genes contain large introns.
The total number of noncoding genes in the human genome is controversial. Some scientists think that there are only about 5,000 noncoding genes while others believe that there may be more than 100,000 (see the article on Non-coding RNA). The difference is largely due to debate over the number of lncRNA genes.
Promoters and regulatory elements
Promoters are DNA segments near the 5' end of the gene where transcription begins. They are the sites where RNA polymerase binds to initiate RNA synthesis. Every gene has a noncoding promoter. | Non-coding DNA | Wikipedia | 499 | 44284 | https://en.wikipedia.org/wiki/Non-coding%20DNA | Biology and health sciences | Molecular biology | Biology |
Regulatory elements are sites that control the transcription of a nearby gene. They are almost always sequences where transcription factors bind to DNA and these transcription factors can either activate transcription (activators) or repress transcription (repressors). Regulatory elements were discovered in the 1960s and their general characteristics were worked out in the 1970s by studying specific transcription factors in bacteria and bacteriophage.
Promoters and regulatory sequences represent an abundant class of noncoding DNA but they mostly consist of a collection of relatively short sequences so they do not take up a very large fraction of the genome. The exact amount of regulatory DNA in mammalian genome is unclear because it is difficult to distinguish between spurious transcription factor binding sites and those that are functional. The binding characteristics of typical DNA-binding proteins were characterized in the 1970s and the biochemical properties of transcription factors predict that in cells with large genomes, the majority of binding sites will not be biologically functional.
Many regulatory sequences occur near promoters, usually upstream of the transcription start site of the gene. Some occur within a gene and a few are located downstream of the transcription termination site. In eukaryotes, there are some regulatory sequences that are located at a considerable distance from the promoter region. These distant regulatory sequences are often called enhancers but there is no rigorous definition of enhancer that distinguishes it from other transcription factor binding sites.
Introns
Introns are the parts of a gene that are transcribed into the precursor RNA sequence, but ultimately removed by RNA splicing during the processing to mature RNA. Introns are found in both types of genes: protein-coding genes and noncoding genes. They are present in prokaryotes but they are much more common in eukaryotic genomes.
Group I and group II introns take up only a small percentage of the genome when they are present. Spliceosomal introns (see Figure) are only found in eukaryotes and they can represent a substantial proportion of the genome. In humans, for example, introns in protein-coding genes cover 37% of the genome. Combining that with about 1% coding sequences means that protein-coding genes occupy about 38% of the human genome. The calculations for noncoding genes are more complicated because there is considerable dispute over the total number of noncoding genes but taking only the well-defined examples means that noncoding genes occupy at least 6% of the genome.
Untranslated regions | Non-coding DNA | Wikipedia | 495 | 44284 | https://en.wikipedia.org/wiki/Non-coding%20DNA | Biology and health sciences | Molecular biology | Biology |
The standard biochemistry and molecular biology textbooks describe non-coding nucleotides in mRNA located between the 5' end of the gene and the translation initiation codon. These regions are called 5'-untranslated regions or 5'-UTRs. Similar regions called 3'-untranslated regions (3'-UTRs) are found at the end of the gene. The 5'-UTRs and 3'UTRs are very short in bacteria but they can be several hundred nucleotides in length in eukaryotes. They contain short elements that control the initiation of translation (5'-UTRs) and transcription termination (3'-UTRs) as well as regulatory elements that may control mRNA stability, processing, and targeting to different regions of the cell.
Origins of replication
DNA synthesis begins at specific sites called origins of replication. These are regions of the genome where the DNA replication machinery is assembled and the DNA is unwound to begin DNA synthesis. In most cases, replication proceeds in both directions from the replication origin.
The main features of replication origins are sequences where specific initiation proteins are bound. A typical replication origin covers about 100-200 base pairs of DNA. Prokaryotes have one origin of replication per chromosome or plasmid but there are usually multiple origins in eukaryotic chromosomes. The human genome contains about 100,000 origins of replication representing about 0.3% of the genome.
Centromeres
Centromeres are the sites where spindle fibers attach to newly replicated chromosomes in order to segregate them into daughter cells when the cell divides. Each eukaryotic chromosome has a single functional centromere that is seen as a constricted region in a condensed metaphase chromosome. Centromeric DNA consists of a number of repetitive DNA sequences that often take up a significant fraction of the genome because each centromere can be millions of base pairs in length. In humans, for example, the sequences of all 24 centromeres have been determined and they account for about 6% of the genome. However, it is unlikely that all of this noncoding DNA is essential since there is considerable variation in the total amount of centromeric DNA in different individuals. Centromeres are another example of functional noncoding DNA sequences that have been known for almost half a century and it is likely that they are more abundant than coding DNA.
Telomeres | Non-coding DNA | Wikipedia | 489 | 44284 | https://en.wikipedia.org/wiki/Non-coding%20DNA | Biology and health sciences | Molecular biology | Biology |
Telomeres are regions of repetitive DNA at the end of a chromosome, which provide protection from chromosomal deterioration during DNA replication. Recent studies have shown that telomeres function to aid in its own stability. Telomeric repeat-containing RNA (TERRA) are transcripts derived from telomeres. TERRA has been shown to maintain telomerase activity and lengthen the ends of chromosomes.
Scaffold attachment regions
Both prokaryotic and eukarotic genomes are organized into large loops of protein-bound DNA. In eukaryotes, the bases of the loops are called scaffold attachment regions (SARs) and they consist of stretches of DNA that bind an RNA/protein complex to stabilize the loop. There are about 100,000 loops in the human genome and each SAR consists of about 100 bp of DNA, so the total amount of DNA devoted to SARs accounts for about 0.3% of the human genome.
Pseudogenes
Pseudogenes are mostly former genes that have become non-functional due to mutation, but the term also refers to inactive DNA sequences that are derived from RNAs produced by functional genes (processed pseudogenes). Pseudogenes are only a small fraction of noncoding DNA in prokaryotic genomes because they are eliminated by negative selection. In some eukaryotes, however, pseudogenes can accumulate because selection is not powerful enough to eliminate them (see Nearly neutral theory of molecular evolution).
The human genome contains about 15,000 pseudogenes derived from protein-coding genes and an unknown number derived from noncoding genes. They may cover a substantial fraction of the genome (~5%) since many of them contain former intron sequences.
Pseudogenes are junk DNA by definition and they evolve at the neutral rate as expected for junk DNA. Some former pseudogenes have secondarily acquired a function and this leads some scientists to speculate that most pseudogenes are not junk because they have a yet-to-be-discovered function.
Repeat sequences, transposons and viral elements | Non-coding DNA | Wikipedia | 422 | 44284 | https://en.wikipedia.org/wiki/Non-coding%20DNA | Biology and health sciences | Molecular biology | Biology |
Transposons and retrotransposons are mobile genetic elements. Retrotransposon repeated sequences, which include long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), account for a large proportion of the genomic sequences in many species. Alu sequences, classified as a short interspersed nuclear element, are the most abundant mobile elements in the human genome. Some examples have been found of SINEs exerting transcriptional control of some protein-encoding genes.
Endogenous retrovirus sequences are the product of reverse transcription of retrovirus genomes into the genomes of germ cells. Mutation within these retro-transcribed sequences can inactivate the viral genome.
Over 8% of the human genome is made up of (mostly decayed) endogenous retrovirus sequences, as part of the over 42% fraction that is recognizably derived of retrotransposons, while another 3% can be identified to be the remains of DNA transposons. Much of the remaining half of the genome that is currently without an explained origin is expected to have found its origin in transposable elements that were active so long ago (> 200 million years) that random mutations have rendered them unrecognizable. Genome size variation in at least two kinds of plants is mostly the result of retrotransposon sequences.
Highly repetitive DNA
Highly repetitive DNA consists of short stretches of DNA that are repeated many times in tandem (one after the other). The repeat segments are usually between 2 bp and 10 bp but longer ones are known. Highly repetitive DNA is rare in prokaryotes but common in eukaryotes, especially those with large genomes. It is sometimes called satellite DNA.
Most of the highly repetitive DNA is found in centromeres and telomeres (see above) and most of it is functional although some might be redundant. The other significant fraction resides in short tandem repeats (STRs; also called microsatellites) consisting of short stretches of a simple repeat such as ATC. There are about 350,000 STRs in the human genome and they are scattered throughout the genome with an average length of about 25 repeats.
Variations in the number of STR repeats can cause genetic diseases when they lie within a gene but most of these regions appear to be non-functional junk DNA where the number of repeats can vary considerably from individual to individual. This is why these length differences are used extensively in DNA fingerprinting.
Junk DNA | Non-coding DNA | Wikipedia | 506 | 44284 | https://en.wikipedia.org/wiki/Non-coding%20DNA | Biology and health sciences | Molecular biology | Biology |
Junk DNA is DNA that has no biologically relevant function such as pseudogenes and fragments of once active transposons. Bacteria and viral genomes have very little junk DNA but some eukaryotic genomes may have a substantial amount of junk DNA. The exact amount of nonfunctional DNA in humans and other species with large genomes has not been determined and there is considerable controversy in the scientific literature.
The nonfunctional DNA in bacterial genomes is mostly located in the intergenic fraction of non-coding DNA but in eukaryotic genomes it may also be found within introns. There are many examples of functional DNA elements in non-coding DNA, and it is erroneous to equate non-coding DNA with junk DNA.
Genome-wide association studies (GWAS) and non-coding DNA
Genome-wide association studies (GWAS) identify linkages between alleles and observable traits such as phenotypes and diseases. Most of the associations are between single-nucleotide polymorphisms (SNPs) and the trait being examined and most of these SNPs are located in non-functional DNA. The association establishes a linkage that helps map the DNA region responsible for the trait but it does not necessarily identify the mutations causing the disease or phenotypic difference.
SNPs that are tightly linked to traits are the ones most likely to identify a causal mutation. (The association is referred to as tight linkage disequilibrium.) About 12% of these polymorphisms are found in coding regions; about 40% are located in introns; and most of the rest are found in intergenic regions, including regulatory sequences. | Non-coding DNA | Wikipedia | 347 | 44284 | https://en.wikipedia.org/wiki/Non-coding%20DNA | Biology and health sciences | Molecular biology | Biology |
DNA profiling (also called DNA fingerprinting and genetic fingerprinting) is the process of determining an individual's deoxyribonucleic acid (DNA) characteristics. DNA analysis intended to identify a species, rather than an individual, is called DNA barcoding.
DNA profiling is a forensic technique in criminal investigations, comparing criminal suspects' profiles to DNA evidence so as to assess the likelihood of their involvement in the crime. It is also used in paternity testing, to establish immigration eligibility, and in genealogical and medical research. DNA profiling has also been used in the study of animal and plant populations in the fields of zoology, botany, and agriculture.
Background
Starting in the mid 1970s, scientific advances allowed the use of DNA as a material for the identification of an individual. The first patent covering the direct use of DNA variation for forensics (US5593832A) was filed by Jeffrey Glassberg in 1983, based upon work he had done while at Rockefeller University in the United States in 1981.
British geneticist Sir Alec Jeffreys independently developed a process for DNA profiling in 1984 while working in the Department of Genetics at the University of Leicester. Jeffreys discovered that a DNA examiner could establish patterns in unknown DNA. These patterns were a part of inherited traits that could be used to advance the field of relationship analysis. These discoveries led to the first use of DNA profiling in a criminal case. | DNA profiling | Wikipedia | 290 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
The process, developed by Jeffreys in conjunction with Peter Gill and Dave Werrett of the Forensic Science Service (FSS), was first used forensically in the solving of the murder of two teenagers who had been raped and murdered in Narborough, Leicestershire in 1983 and 1986. In the murder inquiry, led by Detective David Baker, the DNA contained within blood samples obtained voluntarily from around 5,000 local men who willingly assisted Leicestershire Constabulary with the investigation, resulted in the exoneration of Richard Buckland, an initial suspect who had confessed to one of the crimes, and the subsequent conviction of Colin Pitchfork on January 2, 1988. Pitchfork, a local bakery employee, had coerced his coworker Ian Kelly to stand in for him when providing a blood sample—Kelly then used a forged passport to impersonate Pitchfork. Another coworker reported the deception to the police. Pitchfork was arrested, and his blood was sent to Jeffreys' lab for processing and profile development. Pitchfork's profile matched that of DNA left by the murderer which confirmed Pitchfork's presence at both crime scenes; he pleaded guilty to both murders. After some years, a chemical company named Imperial Chemical Industries (ICI) introduced the first ever commercially available kit to the world. Despite being a relatively recent field, it had a significant global influence on both criminal justice system and society.
Although 99.9% of human DNA sequences are the same in every person, enough of the DNA is different that it is possible to distinguish one individual from another, unless they are monozygotic (identical) twins. DNA profiling uses repetitive sequences that are highly variable, called variable number tandem repeats (VNTRs), in particular short tandem repeats (STRs), also known as microsatellites, and minisatellites. VNTR loci are similar between closely related individuals, but are so variable that unrelated individuals are unlikely to have the same VNTRs.
Before VNTRs and STRs, people like Jeffreys used a process called restriction fragment length polymorphism (RFLP). This process regularly used large portions of DNA to analyze the differences between two DNA samples. RFLP was among the first technologies used in DNA profiling and analysis. However, as technology has evolved, new technologies, like STR, emerged and took the place of older technology like RFLP. | DNA profiling | Wikipedia | 481 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
The admissibility of DNA evidence in courts was disputed in the United States in the 1980s and 1990s, but has since become more universally accepted due to improved techniques.
Profiling processes
DNA extraction
When a sample such as blood or saliva is obtained, the DNA is only a small part of what is present in the sample. Before the DNA can be analyzed, it must be extracted from the cells and purified. There are many ways this can be accomplished, but all methods follow the same basic procedure. The cell and nuclear membranes need to be broken up to allow the DNA to be free in solution. Once the DNA is free, it can be separated from all other cellular components. After the DNA has been separated in solution, the remaining cellular debris can then be removed from the solution and discarded, leaving only DNA. The most common methods of DNA extraction include organic extraction (also called phenol–chloroform extraction), Chelex extraction, and solid-phase extraction. Differential extraction is a modified version of extraction in which DNA from two different types of cells can be separated from each other before being purified from the solution. Each method of extraction works well in the laboratory, but analysts typically select their preferred method based on factors such as the cost, the time involved, the quantity of DNA yielded, and the quality of DNA yielded.
RFLP analysis | DNA profiling | Wikipedia | 275 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
RFLP stands for restriction fragment length polymorphism and, in terms of DNA analysis, describes a DNA testing method which utilizes restriction enzymes to "cut" the DNA at short and specific sequences throughout the sample. To start off processing in the laboratory, the sample has to first go through an extraction protocol, which may vary depending on the sample type or laboratory SOPs (Standard Operating Procedures). Once the DNA has been "extracted" from the cells within the sample and separated away from extraneous cellular materials and any nucleases that would degrade the DNA, the sample can then be introduced to the desired restriction enzymes to be cut up into discernable fragments. Following the enzyme digestion, a Southern Blot is performed. Southern Blots are a size-based separation method that are performed on a gel with either radioactive or chemiluminescent probes. RFLP could be conducted with single-locus or multi-locus probes (probes which target either one location on the DNA or multiple locations on the DNA). Incorporating the multi-locus probes allowed for higher discrimination power for the analysis, however completion of this process could take several days to a week for one sample due to the extreme amount of time required by each step required for visualization of the probes.
Polymerase chain reaction (PCR) analysis
This technique was developed in 1983 by Kary Mullis. PCR is now a common and important technique used in medical and biological research labs for a variety of applications.
PCR, or Polymerase Chain Reaction, is a widely used molecular biology technique to amplify a specific DNA sequence.
Amplification is achieved by a series of three steps:
1- Denaturation : In this step, the DNA is heated to 95 °C to dissociate the hydrogen bonds between the complementary base pairs of the double-stranded DNA.
2-Annealing : During this stage the reaction is cooled to 50-65 °C . This enables the primers to attach to a specific location on the single -stranded template DNA by way of hydrogen bonding.
3-Extension : A thermostable DNA polymerase which is Taq polymerase is commonly used at this step. This is done at a temperature of 72 °C . DNA polymerase adds nucleotides in the 5'-3' direction and synthesizes the complementary strand of the DNA template .
STR analysis
The system of DNA profiling used today is based on polymerase chain reaction (PCR) and uses simple sequences. | DNA profiling | Wikipedia | 511 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
From country to country, different STR-based DNA-profiling systems are in use. In North America, systems that amplify the CODIS 20 core loci are almost universal, whereas in the United Kingdom the DNA-17 loci system is in use, and Australia uses 18 core markers.
The true power of STR analysis is in its statistical power of discrimination. Because the 20 loci that are currently used for discrimination in CODIS are independently assorted (having a certain number of repeats at one locus does not change the likelihood of having any number of repeats at any other locus), the product rule for probabilities can be applied. This means that, if someone has the DNA type of ABC, where the three loci were independent, then the probability of that individual having that DNA type is the probability of having type A times the probability of having type B times the probability of having type C. This has resulted in the ability to generate match probabilities of 1 in a quintillion (1x1018) or more. However, DNA database searches showed much more frequent than expected false DNA profile matches.
Y-chromosome analysis
Due to the paternal inheritance, Y-haplotypes provide information about the genetic ancestry of the male population. To investigate this population history, and to provide estimates for haplotype frequencies in criminal casework, the "Y haplotype reference database (YHRD)" has been created in 2000 as an online resource. It currently comprises more than 300,000 minimal (8 locus) haplotypes from world-wide populations.
Mitochondrial analysis
mtDNA can be obtained from such material as hair shafts and old bones/teeth. Control mechanism based on interaction point with data. This can be determined by tooled placement in sample.
Issues with forensic DNA samples
When people think of DNA analysis, they often think about television shows like NCIS or CSI, which portray DNA samples coming into a lab and being instantly analyzed, followed by the pulling up of a picture of the suspect within minutes. However, the reality is quite different, and perfect DNA samples are often not collected from the scene of a crime. Homicide victims are frequently left exposed to harsh conditions before they are found, and objects that are used to commit crimes have often been handled by more than one person. The two most prevalent issues that forensic scientists encounter when analyzing DNA samples are degraded samples and DNA mixtures. | DNA profiling | Wikipedia | 491 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Degraded DNA
Before modern PCR methods existed, it was almost impossible to analyze degraded DNA samples. Methods like restriction fragment length polymorphism (RFLP), which was the first technique used for DNA analysis in forensic science, required high molecular weight DNA in the sample in order to get reliable data. High molecular weight DNA, however, is lacking in degraded samples, as the DNA is too fragmented to carry out RFLP accurately. It was only when polymerase chain reaction techniques were invented that analysis of degraded DNA samples were able to be carried out. Multiplex PCR in particular made it possible to isolate and to amplify the small fragments of DNA that are still left in degraded samples. When multiplex PCR methods are compared to the older methods like RFLP, a vast difference can be seen. Multiplex PCR can theoretically amplify less than 1 ng of DNA, but RFLP had to have a least 100 ng of DNA in order to carry out an analysis. | DNA profiling | Wikipedia | 197 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Low-template DNA can happen when there is less than 0.1 ng() of DNA in a sample. This can lead to more stochastic effects (random events) such as allelic dropout or allelic drop-in which can alter the interpretation of a DNA profile. These stochastic effects can lead to the unequal amplification of the 2 alleles that come from a heterozygous individual. It is especially important to take low-template DNA into account when dealing with a mixture of DNA sample. This is because for one (or more) of the contributors in the mixture, they are more likely to have less than the optimal amount of DNA for the PCR reaction to work properly. Therefore, stochastic thresholds are developed for DNA profile interpretation. The stochastic threshold is the minimum peak height (RFU value), seen in an electropherogram where dropout occurs. If the peak height value is above this threshold, then it is reasonable to assume that allelic dropout has not occurred. For example, if only 1 peak is seen for a particular locus in the electropherogram but its peak height is above the stochastic threshold, then we can reasonably assume that this individual is homozygous and is not missing its heterozygous partner allele that otherwise would have dropped out due to having low-template DNA. Allelic dropout can occur when there is low-template DNA because there is such little DNA to start with that at this locus the contributor to the DNA sample (or mixture) is a true heterozygote but the other allele is not amplified and so it would be lost. Allelic drop-in can also occur when there is low-template DNA because sometimes the stutter peak can be amplified. The stutter is an artifact of PCR. During the PCR reaction, DNA Polymerase will come in and add nucleotides off of the primer, but this whole process is very dynamic, meaning that the DNA Polymerase is constantly binding, popping off and then rebinding. Therefore, sometimes DNA Polymerase will rejoin at the short tandem repeat ahead of it, leading to a short tandem repeat that is 1 repeat less than the template | DNA profiling | Wikipedia | 465 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
During PCR, if DNA Polymerase happens to bind to a locus in stutter and starts to amplify it to make lots of copies, then this stutter product will appear randomly in the electropherogram, leading to allelic drop-in | DNA profiling | Wikipedia | 53 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
MiniSTR analysis
In instances in which DNA samples are degraded, like if there are intense fires or all that remains are bone fragments, standard STR testing on those samples can be inadequate. When standard STR testing is done on highly degraded samples, the larger STR loci often drop out, and only partial DNA profiles are obtained. Partial DNA profiles can be a powerful tool, but the probability of a random match is larger than if a full profile was obtained. One method that has been developed to analyse degraded DNA samples is to use miniSTR technology. In the new approach, primers are specially designed to bind closer to the STR region.
In normal STR testing, the primers bind to longer sequences that contain the STR region within the segment. MiniSTR analysis, however, targets only the STR location, which results in a DNA product that is much smaller.
By placing the primers closer to the actual STR regions, there is a higher chance that successful amplification of this region will occur. Successful amplification of those STR regions can now occur, and more complete DNA profiles can be obtained. The success that smaller PCR products produce a higher success rate with highly degraded samples was first reported in 1995, when miniSTR technology was used to identify victims of the Waco fire.
DNA mixtures
Mixtures are another common issue faced by forensic scientists when they are analyzing unknown or questionable DNA samples. A mixture is defined as a DNA sample that contains two or more individual contributors. That can often occur when a DNA sample is swabbed from an item that is handled by more than one person or when a sample contains both the victim's and the assailant's DNA. The presence of more than one individual in a DNA sample can make it challenging to detect individual profiles, and interpretation of mixtures should be performed only by highly trained individuals. Mixtures that contain two or three individuals can be interpreted with difficulty. Mixtures that contain four or more individuals are much too convoluted to get individual profiles. One common scenario in which a mixture is often obtained is in the case of sexual assault. A sample may be collected that contains material from the victim, the victim's consensual sexual partners, and the perpetrator(s). | DNA profiling | Wikipedia | 469 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Mixtures can generally be sorted into three categories: Type A, Type B, and Type C. Type A mixtures have alleles with similar peak-heights all around, so the contributors cannot be distinguished from each other. Type B mixtures can be deconvoluted by comparing peak-height ratios to determine which alleles were donated together. Type C mixtures cannot be safely interpreted with current technology because the samples were affected by DNA degradation or having too small a quantity of DNA present.
When looking at an electropherogram, it is possible to determine the number of contributors in less complex mixtures based on the number of peaks located in each locus. In comparison to a single source profile, which will only have one or two peaks at each locus, a mixture is when there are three or more peaks at two or more loci. If there are three peaks at only a single locus, then it is possible to have a single contributor who is tri-allelic at that locus. Two person mixtures will have between two and four peaks at each locus, and three person mixtures will have between three and six peaks at each locus. Mixtures become increasingly difficult to deconvolute as the number of contributors increases.
As detection methods in DNA profiling advance, forensic scientists are seeing more DNA samples that contain mixtures, as even the smallest contributor can now be detected by modern tests. The ease in which forensic scientists have in interpenetrating DNA mixtures largely depends on the ratio of DNA present from each individual, the genotype combinations, and the total amount of DNA amplified. The DNA ratio is often the most important aspect to look at in determining whether a mixture can be interpreted. For example, if a DNA sample had two contributors, it would be easy to interpret individual profiles if the ratio of DNA contributed by one person was much higher than the second person. When a sample has three or more contributors, it becomes extremely difficult to determine individual profiles. Fortunately, advancements in probabilistic genotyping may make that sort of determination possible in the future. Probabilistic genotyping uses complex computer software to run through thousands of mathematical computations to produce statistical likelihoods of individual genotypes found in a mixture.
DNA profiling in plant: | DNA profiling | Wikipedia | 465 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Plant DNA profiling (fingerprinting) is a method for identifying cultivars that uses molecular marker techniques. This method is gaining attention due to Trade Related Intellectual property rights (TRIPs) and the Convention on Biological Diversity (CBD).
Advantages of Plant DNA profiling:
Identification, authentication, specific distinction, detecting adulteration and identifying phytoconstituents are all possible with DNA fingerprinting in medical plants.
DNA based markers are critical for these applications, determining the future of scientific study in pharmacognosy.
It also helps with determining the traits (such as seed size and leaf color) are likely to improve the offspring or not.
DNA databases
An early application of a DNA database was the compilation of a Mitochondrial DNA Concordance, prepared by Kevin W. P. Miller and John L. Dawson at the University of Cambridge from 1996 to 1999 from data collected as part of Miller's PhD thesis. There are now several DNA databases in existence around the world. Some are private, but most of the largest databases are government-controlled. The United States maintains the largest DNA database, with the Combined DNA Index System (CODIS) holding over 13 million records as of May 2018. The United Kingdom maintains the National DNA Database (NDNAD), which is of similar size, despite the UK's smaller population. The size of this database, and its rate of growth, are giving concern to civil liberties groups in the UK, where police have wide-ranging powers to take samples and retain them even in the event of acquittal. The Conservative–Liberal Democrat coalition partially addressed these concerns with part 1 of the Protection of Freedoms Act 2012, under which DNA samples must be deleted if suspects are acquitted or not charged, except in relation to certain (mostly serious or sexual) offenses. Public discourse around the introduction of advanced forensic techniques (such as genetic genealogy using public genealogy databases and DNA phenotyping approaches) has been limited, disjointed, unfocused, and raises issues of privacy and consent that may warrant the establishment of additional legal protections.
The U.S. Patriot Act of the United States provides a means for the U.S. government to get DNA samples from suspected terrorists. DNA information from crimes is collected and deposited into the CODIS database, which is maintained by the FBI. CODIS enables law enforcement officials to test DNA samples from crimes for matches within the database, providing a means of finding specific biological profiles associated with collected DNA evidence. | DNA profiling | Wikipedia | 505 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
When a match is made from a national DNA databank to link a crime scene to an offender having provided a DNA sample to a database, that link is often referred to as a cold hit. A cold hit is of value in referring the police agency to a specific suspect but is of less evidential value than a DNA match made from outside the DNA Databank.
FBI agents cannot legally store DNA of a person not convicted of a crime. DNA collected from a suspect not later convicted must be disposed of and not entered into the database. In 1998, a man residing in the UK was arrested on accusation of burglary. His DNA was taken and tested, and he was later released. Nine months later, this man's DNA was accidentally and illegally entered in the DNA database. New DNA is automatically compared to the DNA found at cold cases and, in this case, this man was found to be a match to DNA found at a rape and assault case one year earlier. The government then prosecuted him for these crimes. During the trial the DNA match was requested to be removed from the evidence because it had been illegally entered into the database. The request was carried out.
The DNA of the perpetrator, collected from victims of rape, can be stored for years until a match is found. In 2014, to address this problem, Congress extended a bill that helps states deal with "a backlog" of evidence.
DNA profiling databases in Plants:
PIDS:
PIDS(Plant international DNA-fingerprinting system) is an open source web server and free software based plant international DNA fingerprinting system.
It manages huge amount of microsatellite DNA fingerprint data, performs genetic studies, and automates collection, storage and maintenance while decreasing human error and increasing efficiency.
The system may be tailored to specific laboratory needs, making it a valuable tool for plant breeders, forensic science, and human fingerprint recognition.
It keeps track of experiments, standardizes data and promotes inter-database communication.
It also helps with the regulation of variety quality, the preservation of variety rights and the use of molecular markers in breeding by providing location statistics, merging, comparison and genetic analysis function. | DNA profiling | Wikipedia | 439 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Considerations in evaluating DNA evidence
When using RFLP, the theoretical risk of a coincidental match is 1 in 100 billion (100,000,000,000) although the practical risk is actually 1 in 1,000 because monozygotic twins are 0.2% of the human population. Moreover, the rate of laboratory error is almost certainly higher than that and actual laboratory procedures often do not reflect the theory under which the coincidence probabilities were computed. For example, coincidence probabilities may be calculated based on the probabilities that markers in two samples have bands in precisely the same location, but a laboratory worker may conclude that similar but not precisely-identical band patterns result from identical genetic samples with some imperfection in the agarose gel. However, in that case, the laboratory worker increases the coincidence risk by expanding the criteria for declaring a match. Studies conducted in the 2000s quoted relatively-high error rates, which may be cause for concern. In the early days of genetic fingerprinting, the necessary population data to compute a match probability accurately was sometimes unavailable. Between 1992 and 1996, arbitrary-low ceilings were controversially put on match probabilities used in RFLP analysis, rather than the higher theoretically computed ones.
Evidence of genetic relationship
It is possible to use DNA profiling as evidence of genetic relationship although such evidence varies in strength from weak to positive. Testing that shows no relationship is absolutely certain. Further, while almost all individuals have a single and distinct set of genes, ultra-rare individuals, known as "chimeras", have at least two different sets of genes. There have been two cases of DNA profiling that falsely suggested that a mother was unrelated to her children.
Fake DNA evidence
The functional analysis of genes and their coding sequences (open reading frames [ORFs]) typically requires that each ORF be expressed, the encoded protein purified, antibodies produced, phenotypes examined, intracellular localization determined, and interactions with other proteins sought. In a study conducted by the life science company Nucleix and published in the journal Forensic Science International, scientists found that an in vitro synthesized sample of DNA matching any desired genetic profile can be constructed using standard molecular biology techniques without obtaining any actual tissue from that person.
DNA evidence in criminal trials | DNA profiling | Wikipedia | 459 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Familial DNA searching
Familial DNA searching (sometimes referred to as "familial DNA" or "familial DNA database searching") is the practice of creating new investigative leads in cases where DNA evidence found at the scene of a crime (forensic profile) strongly resembles that of an existing DNA profile (offender profile) in a state DNA database but there is not an exact match. After all other leads have been exhausted, investigators may use specially developed software to compare the forensic profile to all profiles taken from a state's DNA database to generate a list of those offenders already in the database who are most likely to be a very close relative of the individual whose DNA is in the forensic profile. | DNA profiling | Wikipedia | 146 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Familial DNA database searching was first used in an investigation leading to the conviction of Jeffrey Gafoor of the murder of Lynette White in the United Kingdom on 4 July 2003. DNA evidence was matched to Gafoor's nephew, who at 14 years old had not been born at the time of the murder in 1988. It was used again in 2004 to find a man who threw a brick from a motorway bridge and hit a lorry driver, killing him. DNA found on the brick matched that found at the scene of a car theft earlier in the day, but there were no good matches on the national DNA database. A wider search found a partial match to an individual; on being questioned, this man revealed he had a brother, Craig Harman, who lived very close to the original crime scene. Harman voluntarily submitted a DNA sample, and confessed when it matched the sample from the brick. As of 2011, familial DNA database searching is not conducted on a national level in the United States, where states determine how and when to conduct familial searches. The first familial DNA search with a subsequent conviction in the United States was conducted in Denver, Colorado, in 2008, using software developed under the leadership of Denver District Attorney Mitch Morrissey and Denver Police Department Crime Lab Director Gregg LaBerge. California was the first state to implement a policy for familial searching under then-Attorney General Jerry Brown, who later became Governor. In his role as consultant to the Familial Search Working Group of the California Department of Justice, former Alameda County Prosecutor Rock Harmon is widely considered to have been the catalyst in the adoption of familial search technology in California. The technique was used to catch the Los Angeles serial killer known as the "Grim Sleeper" in 2010. It was not a witness or informant that tipped off law enforcement to the identity of the "Grim Sleeper" serial killer, who had eluded police for more than two decades, but DNA from the suspect's own son. The suspect's son had been arrested and convicted in a felony weapons charge and swabbed for DNA the year before. When his DNA was entered into the database of convicted felons, detectives were alerted to a partial match to evidence found at the "Grim Sleeper" crime scenes. David Franklin Jr., also known as the Grim Sleeper, was charged with ten counts of murder and one count of attempted murder | DNA profiling | Wikipedia | 499 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
More recently, familial DNA led to the arrest of 21-year-old Elvis Garcia on charges of sexual assault and false imprisonment of a woman in Santa Cruz in 2008. In March 2011 Virginia Governor Bob McDonnell announced that Virginia would begin using familial DNA searches | DNA profiling | Wikipedia | 56 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
At a press conference in Virginia on 7 March 2011, regarding the East Coast Rapist, Prince William County prosecutor Paul Ebert and Fairfax County Police Detective John Kelly said the case would have been solved years ago if Virginia had used familial DNA searching. Aaron Thomas, the suspected East Coast Rapist, was arrested in connection with the rape of 17 women from Virginia to Rhode Island, but familial DNA was not used in the case.
Critics of familial DNA database searches argue that the technique is an invasion of an individual's 4th Amendment rights. Privacy advocates are petitioning for DNA database restrictions, arguing that the only fair way to search for possible DNA matches to relatives of offenders or arrestees would be to have a population-wide DNA database. Some scholars have pointed out that the privacy concerns surrounding familial searching are similar in some respects to other police search techniques, and most have concluded that the practice is constitutional. The Ninth Circuit Court of Appeals in United States v. Pool (vacated as moot) suggested that this practice is somewhat analogous to a witness looking at a photograph of one person and stating that it looked like the perpetrator, which leads law enforcement to show the witness photos of similar looking individuals, one of whom is identified as the perpetrator.
Critics also state that racial profiling could occur on account of familial DNA testing. In the United States, the conviction rates of racial minorities are much higher than that of the overall population. It is unclear whether this is due to discrimination from police officers and the courts, as opposed to a simple higher rate of offence among minorities. Arrest-based databases, which are found in the majority of the United States, lead to an even greater level of racial discrimination. An arrest, as opposed to conviction, relies much more heavily on police discretion.
For instance, investigators with Denver District Attorney's Office successfully identified a suspect in a property theft case using a familial DNA search. In this example, the suspect's blood left at the scene of the crime strongly resembled that of a current Colorado Department of Corrections prisoner. | DNA profiling | Wikipedia | 429 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Partial matches
Partial DNA matches are the result of moderate stringency CODIS searches that produce a potential match that shares at least one allele at every locus. Partial matching does not involve the use of familial search software, such as those used in the United Kingdom and the United States, or additional Y-STR analysis and therefore often misses sibling relationships. Partial matching has been used to identify suspects in several cases in both countries and has also been used as a tool to exonerate the falsely accused. Darryl Hunt was wrongly convicted in connection with the rape and the murder of a young woman in 1984 in North Carolina.
Surreptitious DNA collecting
Police forces may collect DNA samples without a suspect's knowledge, and use it as evidence. The legality of the practice has been questioned in Australia.
In the United States, where it has been accepted, courts often rule that there is no expectation of privacy and cite California v. Greenwood (1988), in which the Supreme Court held that the Fourth Amendment does not prohibit the warrantless search and seizure of garbage left for collection outside the curtilage of a home. Critics of this practice underline that this analogy ignores that "most people have no idea that they risk surrendering their genetic identity to the police by, for instance, failing to destroy a used coffee cup. Moreover, even if they do realize it, there is no way to avoid abandoning one's DNA in public."
The United States Supreme Court ruled in Maryland v. King (2013) that DNA sampling of prisoners arrested for serious crimes is constitutional.
In the United Kingdom, the Human Tissue Act 2004 prohibits private individuals from covertly collecting biological samples (hair, fingernails, etc.) for DNA analysis but exempts medical and criminal investigations from the prohibition.
England and Wales
Evidence from an expert who has compared DNA samples must be accompanied by evidence as to the sources of the samples and the procedures for obtaining the DNA profiles. The judge must ensure that the jury must understand the significance of DNA matches and mismatches in the profiles. The judge must also ensure that the jury does not confuse the match probability (the probability that a person that is chosen at random has a matching DNA profile to the sample from the scene) with the probability that a person with matching DNA committed the crime. In 1996 R v. Doheny | DNA profiling | Wikipedia | 473 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Juries should weigh up conflicting and corroborative evidence, using their own common sense and not by using mathematical formulae, such as Bayes' theorem, so as to avoid "confusion, misunderstanding and misjudgment".
Presentation and evaluation of evidence of partial or incomplete DNA profiles
In R v Bates, Moore-Bick LJ said:
DNA testing in the United States
There are state laws on DNA profiling in all 50 states of the United States. Detailed information on database laws in each state can be found at the National Conference of State Legislatures website.
Development of artificial DNA
In August 2009, scientists in Israel raised serious doubts concerning the use of DNA by law enforcement as the ultimate method of identification. In a paper published in the journal Forensic Science International: Genetics, the Israeli researchers demonstrated that it is possible to manufacture DNA in a laboratory, thus falsifying DNA evidence. The scientists fabricated saliva and blood samples, which originally contained DNA from a person other than the supposed donor of the blood and saliva.
The researchers also showed that, using a DNA database, it is possible to take information from a profile and manufacture DNA to match it, and that this can be done without access to any actual DNA from the person whose DNA they are duplicating. The synthetic DNA oligos required for the procedure are common in molecular laboratories.
The New York Times quoted the lead author, Daniel Frumkin, saying, "You can just engineer a crime scene ... any biology undergraduate could perform this". Frumkin perfected a test that can differentiate real DNA samples from fake ones. His test detects epigenetic modifications, in particular, DNA methylation. Seventy percent of the DNA in any human genome is methylated, meaning it contains methyl group modifications within a CpG dinucleotide context. Methylation at the promoter region is associated with gene silencing. The synthetic DNA lacks this epigenetic modification, which allows the test to distinguish manufactured DNA from genuine DNA.
It is unknown how many police departments, if any, currently use the test. No police lab has publicly announced that it is using the new test to verify DNA results.
Researchers at the University of Tokyo integrated an artificial DNA replication scheme with a rebuilt gene expression system and micro-compartmentalization utilizing cell-free materials alone for the first time. Multiple cycles of serial dilution were performed on a system contained in microscale water-in-oil droplets.
Chances of making DNA change on purpose | DNA profiling | Wikipedia | 505 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Overall, this study's artificial genomic DNA, which kept copying itself using self-encoded proteins and made its sequence better on its own, is a good starting point for making more complex artificial cells. By adding the genes needed for transcription and translation to artificial genomic DNA, it may be possible in the future to make artificial cells that can grow on their own when fed small molecules like amino acids and nucleotides. Using living organisms to make useful things, like drugs and food, would be more stable and easier to control in these artificial cells.
On July 7, 2008, the American chemical society reported that Japanese chemists have created the world's first DNA molecule comprised nearly completely of synthetic components.
A nano-particle based artificial transcription factor for gene regulation:
Nano Script is a nanoparticle-based artificial transcription factor that is supposed to replicate the structure and function of TFs. On gold nanoparticles, functional peptides and tiny molecules referred to as synthetic transcription factors, which imitate the various TF domains, were attached to create Nano Script. We show that Nano Script localizes to the nucleus and begins transcription of a reporter plasmid by an amount more than 15-fold. Moreover, Nano Script can successfully transcribe targeted genes onto endogenous DNA in a nonviral manner.
Three different fluorophores—red, green, and blue—were carefully fixed on the DNA rod surface to provide spatial information and create a nanoscale barcode. Epifluorescence and total internal reflection fluorescence microscopy reliably deciphered spatial information between fluorophores. By moving the three fluorophores on the DNA rod, this nanoscale barcode created 216 fluorescence patterns. | DNA profiling | Wikipedia | 354 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
Cases
In 1986, Richard Buckland was exonerated, despite having admitted to the rape and murder of a teenager near Leicester, the city where DNA profiling was first developed. This was the first use of DNA fingerprinting in a criminal investigation, and the first to prove a suspect's innocence. The following year Colin Pitchfork was identified as the perpetrator of the same murder, in addition to another, using the same techniques that had cleared Buckland.
In 1987, genetic fingerprinting was used in a US criminal court for the first time in the trial of a man accused of unlawful intercourse with a mentally disabled 14-year-old female who gave birth to a baby.
In 1987, Florida rapist Tommie Lee Andrews was the first person in the United States to be convicted as a result of DNA evidence, for raping a woman during a burglary; he was convicted on 6 November 1987, and sentenced to 22 years in prison.
In 1990, a violent murder of a young student in Brno was the first criminal case in Czechoslovakia solved by DNA evidence, with the murderer sentenced to 23 years in prison.
In 1992, DNA from a palo verde tree was used to convict Mark Alan Bogan of murder. DNA from seed pods of a tree at the crime scene was found to match that of seed pods found in Bogan's truck. This is the first instance of plant DNA admitted in a criminal case.
In 1994, the claim that Anna Anderson was Grand Duchess Anastasia Nikolaevna of Russia was tested after her death using samples of her tissue that had been stored at a Charlottesville hospital following a medical procedure. The tissue was tested using DNA fingerprinting, and showed that she bore no relation to the Romanovs.
In 1994, Earl Washington, Jr., of Virginia had his death sentence commuted to life imprisonment a week before his scheduled execution date based on DNA evidence. He received a full pardon in 2000 based on more advanced testing.
In 1999, Raymond Easton, a disabled man from Swindon, England, was arrested and detained for seven hours in connection with a burglary. He was released due to an inaccurate DNA match. His DNA had been retained on file after an unrelated domestic incident some time previously. | DNA profiling | Wikipedia | 451 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
In 2000 Frank Lee Smith was proved innocent by DNA profiling of the murder of an eight-year-old girl after spending 14 years on death row in Florida, USA. However he had died of cancer just before his innocence was proven. In view of this the Florida state governor ordered that in future any death row inmate claiming innocence should have DNA testing.
In May 2000 Gordon Graham murdered Paul Gault at his home in Lisburn, Northern Ireland. Graham was convicted of the murder when his DNA was found on a sports bag left in the house as part of an elaborate ploy to suggest the murder occurred after a burglary had gone wrong. Graham was having an affair with the victim's wife at the time of the murder. It was the first time Low Copy Number DNA was used in Northern Ireland.
In 2001, Wayne Butler was convicted for the murder of Celia Douty. It was the first murder in Australia to be solved using DNA profiling.
In 2002, the body of James Hanratty, hanged in 1962 for the "A6 murder", was exhumed and DNA samples from the body and members of his family were analysed. The results convinced Court of Appeal judges that Hanratty's guilt, which had been strenuously disputed by campaigners, was proved "beyond doubt". Paul Foot and some other campaigners continued to believe in Hanratty's innocence and argued that the DNA evidence could have been contaminated, noting that the small DNA samples from items of clothing, kept in a police laboratory for over 40 years "in conditions that do not satisfy modern evidential standards", had had to be subjected to very new amplification techniques in order to yield any genetic profile. However, no DNA other than Hanratty's was found on the evidence tested, contrary to what would have been expected had the evidence indeed been contaminated.
In August 2002, Annalisa Vicentini was shot dead in Tuscany. Bartender Peter Hamkin, 23, was arrested, in Merseyside in March 2003 on an extradition warrant heard at Bow Street Magistrates' Court in London to establish whether he should be taken to Italy to face a murder charge. DNA "proved" he shot her, but he was cleared on other evidence.
In 2003, Welshman Jeffrey Gafoor was convicted of the 1988 murder of Lynette White, when crime scene evidence collected 12 years earlier was re-examined using STR techniques, resulting in a match with his nephew. | DNA profiling | Wikipedia | 507 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
In June 2003, because of new DNA evidence, Dennis Halstead, John Kogut and John Restivo won a re-trial on their murder conviction, their convictions were struck down and they were released.
In 2004, DNA testing shed new light into the mysterious 1912 disappearance of Bobby Dunbar, a four-year-old boy who vanished during a fishing trip. He was allegedly found alive eight months later in the custody of William Cantwell Walters, but another woman claimed that the boy was her son, Bruce Anderson, whom she had entrusted in Walters' custody. The courts disbelieved her claim and convicted Walters for the kidnapping. The boy was raised and known as Bobby Dunbar throughout the rest of his life. However, DNA tests on Dunbar's son and nephew revealed the two were not related, thus establishing that the boy found in 1912 was not Bobby Dunbar, whose real fate remains unknown.
In 2005, Gary Leiterman was convicted of the 1969 murder of Jane Mixer, a law student at the University of Michigan, after DNA found on Mixer's pantyhose was matched to Leiterman. DNA in a drop of blood on Mixer's hand was matched to John Ruelas, who was only four years old in 1969 and was never successfully connected to the case in any other way. Leiterman's defense unsuccessfully argued that the unexplained match of the blood spot to Ruelas pointed to cross-contamination and raised doubts about the reliability of the lab's identification of Leiterman.
In November 2008, Anthony Curcio was arrested for masterminding one of the most elaborately planned armored car heists in history. DNA evidence linked Curcio to the crime.
In March 2009, Sean Hodgson—convicted of 1979 killing of Teresa De Simone, 22, in her car in Southampton—was released after tests proved DNA from the scene was not his. It was later matched to DNA retrieved from the exhumed body of David Lace. Lace had previously confessed to the crime but was not believed by the detectives. He served time in prison for other crimes committed at the same time as the murder and then committed suicide in 1988. | DNA profiling | Wikipedia | 440 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
In 2012, a case of babies being switched, many decades earlier, was discovered by accident. After undertaking DNA testing for other purposes, Alice Collins Plebuch was advised that her ancestry appeared to include a significant Ashkenazi Jewish component, despite a belief in her family that they were of predominantly Irish descent. Profiling of Plebuch's genome suggested that it included distinct and unexpected components associated with Ashkenazi, Middle Eastern, and Eastern European populations. This led Plebuch to conduct an extensive investigation, after which she concluded that her father had been switched (possibly accidentally) with another baby soon after birth. Plebuch was also able to identify the biological ancestors of her father.
In 2016 Anthea Ring, abandoned as a baby, was able to use a DNA sample and DNA matching database to discover her deceased mother's identity and roots in County Mayo, Ireland. A recently developed forensic test was subsequently used to capture DNA from saliva left on old stamps and envelopes by her suspected father, uncovered through painstaking genealogy research. The DNA in the first three samples was too degraded to use. However, on the fourth, more than enough DNA was found. The test, which has a degree of accuracy acceptable in UK courts, proved that a man named Patrick Coyne was her biological father.
In 2018 the Buckskin girl (a body found in 1981 in Ohio) was identified as Marcia King from Arkansas using DNA genealogical techniques
In 2018 Joseph James DeAngelo was arrested as the main suspect for the Golden State Killer using DNA and genealogy techniques.
In 2018, William Earl Talbott II was arrested as a suspect for the 1987 murders of Jay Cook and Tanya Van Cuylenborg with the assistance of genealogical DNA testing. The same genetic genealogist that helped in this case also helped police with 18 other arrests in 2018.
In 2018, With the use of Next Generation Identification System's enhanced biometric capabilities, the FBI matched the fingerprint of a suspect named Timothy David Nelson and arrested him 20 years after the alleged sexual assault. | DNA profiling | Wikipedia | 411 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
DNA evidence as evidence to prove rights of succession to British titles
DNA testing has been used to establish the right of succession to British titles.
Cases:
Baron Moynihan
Pringle baronets | DNA profiling | Wikipedia | 39 | 44290 | https://en.wikipedia.org/wiki/DNA%20profiling | Technology | Diagnostic technologies | null |
A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice sheet. It may consist of partly rounded particles ranging in size from boulders (in which case it is often referred to as boulder clay) down to gravel and sand, in a groundmass of finely-divided clayey material sometimes called glacial flour. Lateral moraines are those formed at the side of the ice flow, and terminal moraines are those formed at the foot, marking the maximum advance of the glacier. Other types of moraine include ground moraines (till-covered areas forming sheets on flat or irregular topography) and medial moraines (moraines formed where two glaciers meet).
Etymology
The word moraine is borrowed from French , which in turn is derived from the Savoyard Italian ('mound of earth'). in this case was derived from Provençal ('snout'), itself from Vulgar Latin ('rounded object'). The term was introduced into geology by Horace Bénédict de Saussure in 1779.
Characteristics
Moraines are landforms composed of glacial till deposited primarily by glacial ice. Glacial till, in turn, is unstratified and unsorted debris ranging in size from silt-sized glacial flour to large boulders. The individual rock fragments are typically sub-angular to rounded in shape. Moraines may be found on the glacier's surface or deposited as piles or sheets of debris where the glacier has melted.
Formation
Moraines may form through a number of processes, depending on the characteristics of sediment, the dynamics on the ice, and the location on the glacier in which the moraine is formed. Moraine forming processes may be loosely divided into passive and active.
Passive processes involve the placing of chaotic supraglacial sediments onto the landscape with limited reworking, typically forming hummocky moraines. These moraines are composed of supraglacial sediments from the ice surface.
Active processes form or rework moraine sediment directly by the movement of ice, known as glaciotectonism. These form push moraines and thrust-block moraines, which are often composed of till and reworked proglacial sediment. | Moraine | Wikipedia | 474 | 44299 | https://en.wikipedia.org/wiki/Moraine | Physical sciences | Glacial landforms | null |
Moraine may also form by the accumulation of sand and gravel deposits from glacial streams emanating from the ice margin. These fan deposits may coalesce to form a long moraine bank marking the ice margin. Several processes may combine to form and rework a single moraine, and most moraines record a continuum of processes. Reworking of moraines may lead to the formation of placer deposits of gold as is the case of southernmost Chile.
Types of moraines
Moraines can be classified either by origin, location with respect to a glacier or former glacier, or by shape.
Lateral moraines
Lateral moraines are parallel ridges of debris deposited along the sides of a glacier. The unconsolidated debris can be deposited on top of the glacier by frost shattering of the valley walls or from tributary streams flowing into the valley, or may be subglacial debris carried to the surface of the glacier, melted out, and transported to the glacier margin.
Lateral moraines can rise up to over the valley floor, can be up to long, and are steeper close to the glacier margin (up to 80 degrees) than further away (where slopes are typically 29 to 36 degrees).
Ground moraines
Ground moraines are till-covered areas with irregular topography and no ridges, often forming gently rolling hills or plains, with relief of less than . Ground moraine is accumulated at the base of the ice as lodgment till with a thin and discontinuous upper layer of supraglacial till deposited as the glacier retreats. It typically is found in the areas between end moraines.
Rogen moraines
Rogen moraines or ribbed moraines are a type of basal moraines that form a series of ribs perpendicular to the ice flow in an ice sheet. The depressions between the ribs are sometimes filled with water, making the Rogen moraines look like tigerstripes on aerial photographs. Rogen moraines are named after Lake Rogen in Härjedalen, Sweden, the landform's type locality.
de Geer moraines
Closely related to Rogen moraines, de Geer moraines are till ridges up to 5m high and 10–50m wide running perpendicular to the ice flow. They occur in large groups in low-lying areas. Named for Gerard De Geer, who first described them in 1889, these moraines may have developed from crevasses underneath the ice sheet. The Kvarken has a very high density of de Geer moraines. | Moraine | Wikipedia | 511 | 44299 | https://en.wikipedia.org/wiki/Moraine | Physical sciences | Glacial landforms | null |
End or terminal moraines
End moraines, or terminal moraines, are ridges of unconsolidated debris deposited at the snout or end of the glacier. They usually reflect the shape of the glacier's terminus. Glaciers act much like a conveyor belt, carrying debris from the top of the glacier to the bottom where it deposits it in end moraines. End moraine size and shape are determined by whether the glacier is advancing, receding or at equilibrium. The longer the terminus of the glacier stays in one place, the more debris accumulate in the moraine. There are two types of end moraines: terminal and recessional. Terminal moraines mark the maximum advance of the glacier. Recessional moraines are small ridges left as a glacier pauses during its retreat. After a glacier retreats, the end moraine may be destroyed by postglacial erosion.
Recessional moraine
Recessional moraines are often observed as a series of transverse ridges running across a valley behind a terminal moraine. They form perpendicular to the lateral moraines that they reside between and are composed of unconsolidated debris deposited by the glacier. They are created during temporary halts in a glacier's retreat.
Arctic push moraines
In permafrost areas an advancing glacier may push up thick layers of frozen sediments at its front. An arctic push moraine will then be formed.
Medial moraine
A medial moraine is a ridge of moraine that runs down the center of a valley floor. It forms when two glaciers meet and the debris on the edges of the adjacent valley sides join and are carried on top of the enlarged glacier. As the glacier melts or retreats, the debris is deposited and a ridge down the middle of the valley floor is created. The Kaskawulsh Glacier in the Kluane National Park, Yukon, has a ridge of medial moraine 1 km wide.
Supraglacial moraines
Supraglacial moraines are created by debris accumulated on top of glacial ice. This debris can accumulate due to ice flow toward the surface in the ablation zone, melting of surface ice or from debris that falls onto the glacier from valley sidewalls. | Moraine | Wikipedia | 445 | 44299 | https://en.wikipedia.org/wiki/Moraine | Physical sciences | Glacial landforms | null |
Washboard moraines
Washboard moraines, also known as minor or corrugated moraines, are low-amplitude geomorphic features caused by glaciers. They consist of low-relief ridges, in height and around apart, accumulated at the base of the ice as lodgment till. The name "washboard moraine" refers to the fact that, from the air, it resembles a washboard.''
Veiki moraine
A Veiki moraine is a kind of hummocky moraine that forms irregular landscapes of ponds and plateaus surrounded by banks. It forms from the irregular melting of ice covered with a thick layer of debris. Veiki moraine is common in northern Sweden and parts of Canada. | Moraine | Wikipedia | 144 | 44299 | https://en.wikipedia.org/wiki/Moraine | Physical sciences | Glacial landforms | null |
The leopard (Panthera pardus) is one of the five extant cat species in the genus Panthera. It has a pale yellowish to dark golden fur with dark spots grouped in rosettes. Its body is slender and muscular reaching a length of with a long tail and a shoulder height of . Males typically weigh , and females .
The leopard was first described in 1758, and several subspecies were proposed in the 19th and 20th centuries. Today, eight subspecies are recognised in its wide range in Africa and Asia. It initially evolved in Africa during the Early Pleistocene, before migrating into Eurasia around the Early–Middle Pleistocene transition. Leopards were formerly present across Europe, but became extinct in the region at around the end of the Late Pleistocene-early Holocene.
The leopard is adapted to a variety of habitats ranging from rainforest to steppe, including arid and montane areas. It is an opportunistic predator, hunting mostly ungulates and primates. It relies on its spotted pattern for camouflage as it stalks and ambushes its prey, which it sometimes drags up a tree. It is a solitary animal outside the mating season and when raising cubs. Females usually give birth to a litter of 2–4 cubs once in 15–24 months. Both male and female leopards typically reach sexual maturity at the age 2–2.5 years.
Listed as Vulnerable on the IUCN Red List, leopard populations are currently threatened by habitat loss and fragmentation, and are declining in large parts of the global range. Leopards have had cultural roles in Ancient Greece, West Africa and modern Western culture. Leopard skins are popular in fashion.
Etymology
The English name "leopard" comes from Old French or Middle French , that derives from Latin and ancient Greek (). could be a compound of (), meaning , and (), meaning . The word originally referred to a cheetah (Acinonyx jubatus).
"Panther" is another common name, derived from Latin and ancient Greek (); The generic name Panthera originates in Latin , a hunting net for catching wild beasts to be used by the Romans in combats. is the masculine singular form.
Taxonomy
Felis pardus was the scientific name proposed by Carl Linnaeus in 1758.
The generic name Panthera was first used by Lorenz Oken in 1816, who included all the known spotted cats into this group.
Oken's classification was not widely accepted, and Felis or Leopardus was used as the generic name until the early 20th century. | Leopard | Wikipedia | 505 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
The leopard was designated as the type species of Panthera by Joel Asaph Allen in 1902.
In 1917, Reginald Innes Pocock also subordinated the tiger (P. tigris), lion (P. leo), and jaguar (P. onca) to Panthera.
Living subspecies
Following Linnaeus' first description, 27 leopard subspecies were proposed by naturalists between 1794 and 1956. Since 1996, only eight subspecies have been considered valid on the basis of mitochondrial analysis. Later analysis revealed a ninth valid subspecies, the Arabian leopard.
In 2017, the Cat Classification Task Force of the Cat Specialist Group recognized the following eight subspecies as valid taxa:
Results of an analysis of molecular variance and pairwise fixation index of 182 African leopard museum specimens showed that some African leopards exhibit higher genetic differences than Asian leopard subspecies.
Evolution
Results of phylogenetic studies based on nuclear DNA and mitochondrial DNA analysis showed that the last common ancestor of the Panthera and Neofelis genera is thought to have lived about . Neofelis diverged about from the Panthera lineage. The tiger diverged about , followed by the snow leopard about and the leopard about . The leopard is a sister taxon to a clade within Panthera, consisting of the lion and the jaguar.
Results of a phylogenetic analysis of chemical secretions amongst cats indicated that the leopard is closely related to the lion.
The geographic origin of the Panthera is most likely northern Central Asia. The leopard-lion clade was distributed in the Asian and African Palearctic since at least the early Pliocene. The leopard-lion clade diverged 3.1–1.95 million years ago. Additionally, a 2016 study revealed that the mitochondrial genomes of the leopard, lion and snow leopard are more similar to each other than their nuclear genomes, indicating that their ancestors hybridized with the snow leopard at some point in their evolution.
The oldest unambiguous fossils of the leopard are from Eastern Africa, dating to around 2 million years ago. | Leopard | Wikipedia | 399 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
Leopard-like fossil bones and teeth possibly dating to the Pliocene were excavated in Perrier in France, northeast of London, and in Valdarno, Italy. Until 1940, similar fossils dating back to the Pleistocene were excavated mostly in loess and caves at 40 sites in Europe, including Furninha Cave near Lisbon, Genista Caves in Gibraltar, and Santander Province in northern Spain to several sites across France, Switzerland, Italy, Austria, Germany, in the north up to Derby in England, in the east to Přerov in the Czech Republic and the Baranya in southern Hungary.
Leopards arrived in Eurasia during the late Early to Middle Pleistocene around 1.2 to 0.6 million years ago.
Four European Pleistocene leopard subspecies were proposed. P. p. begoueni from the beginning of the Early Pleistocene was replaced about by P. p. sickenbergi, which in turn was replaced by P. p. antiqua around 0.3 million years ago. P. p. spelaea is the most recent subspecies that appeared at the beginning of the Late Pleistocene and survived until about 11,000 years ago and possibly into the early Holocene in the Iberian Peninsula.
Leopards depicted in cave paintings in Chauvet Cave provide indirect evidence of leopard presence in Europe.
Leopard fossils dating to the Late Pleistocene were found in Biśnik Cave in south-central Poland.
Fossil remains were also excavated in the Iberian and Italian Peninsula, and in the Balkans.
Leopard fossils dating to the Pleistocene were also excavated in the Japanese archipelago. Leopard fossils were also found in Taiwan.
Hybrids
In 1953, a male leopard and a female lion were crossbred in Hanshin Park in Nishinomiya, Japan. Their offspring known as a leopon was born in 1959 and 1961, all cubs were spotted and bigger than a juvenile leopard. Attempts to mate a leopon with a tigress proved unsuccessful.
Characteristics | Leopard | Wikipedia | 388 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
The leopard's fur is generally soft and thick, notably softer on the belly than on the back. Its skin colour varies between individuals from pale yellowish to dark golden with dark spots grouped in rosettes. Its underbelly is white and its ringed tail is shorter than its body. Its pupils are round. Leopards living in arid regions are pale cream, yellowish to ochraceous and rufous in colour; those living in forests and mountains are much darker and deep golden. Spots fade toward the white underbelly and the insides and lower parts of the legs. Rosettes are circular in East African leopard populations, and tend to be squarish in Southern African and larger in Asian leopard populations. The fur tends to be grayish in colder climates, and dark golden in rainforest habitats. Rosette patterns are unique in each individual. This pattern is thought to be an adaptation to dense vegetation with patchy shadows, where it serves as camouflage.
Its white-tipped tail is about long, white underneath and with spots that form incomplete bands toward the end of the tail.
The guard hairs protecting the basal hairs are short, in face and head, and increase in length toward the flanks and the belly to about . Juveniles have woolly fur that appear to be dark-coloured due to the densely arranged spots.
Its fur tends to grow longer in colder climates.
The leopard's rosettes differ from those of the jaguar, which are darker and with smaller spots inside. The leopard has a diploid chromosome number of 38.
Melanistic leopards are also known as black panthers. Melanism in leopards is caused by a recessive allele and is inherited as a recessive trait.
In India, nine pale and white leopards were reported between 1905 and 1967.
Leopards exhibiting erythrism were recorded between 1990 and 2015 in South Africa's Madikwe Game Reserve and in Mpumalanga. The cause of this morph known as a "strawberry leopard" or "pink panther" is not well understood. | Leopard | Wikipedia | 411 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
Size
The leopard is a slender and muscular cat, with relatively short limbs and a broad head. It is sexually dimorphic with males larger and heavier than females. Males stand at the shoulder, while females are tall. The head-and-body length ranges between with a long tail. Sizes vary geographically. Males typically weigh , and females . Occasionally, large males can grow up to . Leopards from the Cape Province in South Africa are generally smaller, reaching only in males.
The heaviest wild leopard in Southern Africa weighed around , and it measured . In 2016, an Indian leopard killed in Himachal Pradesh measured with an estimated weight of ; it was perhaps the largest known wild leopard in India.
The largest recorded skull of a leopard was found in India in 1920 and measured in basal length, in breadth, and weighed . The skull of an African leopard measured in basal length, and in breadth, and weighed .
Distribution and habitat
The leopard has the largest distribution of all wild cats, occurring widely in Africa and Asia, although populations are fragmented and declining. It inhabits foremost savanna and rainforest, and areas where grasslands, woodlands and riparian forests remain largely undisturbed. It also persists in urban environments, if it is not persecuted, has sufficient prey and patches of vegetation for shelter during the day.
The leopard's range in West Africa is estimated to have drastically declined by 95%, and in the Sahara desert by 97%. In sub-Saharan Africa, it is still numerous and surviving in marginal habitats where other large cats have disappeared. In southeastern Egypt, an individual found killed in 2017 was the first sighting of the leopard in this area in 65 years.
In West Asia, the leopard inhabits remain in the areas of southern and southeastern Anatolia.
Leopard populations in the Arabian Peninsula are small and fragmented. | Leopard | Wikipedia | 363 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
In the Indian subcontinent, the leopard is still relatively abundant, with greater numbers than those of other Panthera species. Some leopard populations in India live quite close to human settlements and even in semi-developed areas. Although adaptable to human disturbances, leopards require healthy prey populations and appropriate vegetative cover for hunting for prolonged survival and thus rarely linger in heavily developed areas. Due to the leopard's stealth, people often remain unaware that it lives in nearby areas. As of 2020, the leopard population within forested habitats in India's tiger range landscapes was estimated at 12,172 to 13,535 individuals. Surveyed landscapes included elevations below in the Shivalik Hills and Gangetic plains, Central India and Eastern Ghats, Western Ghats, the Brahmaputra River basin and hills in Northeast India.
In Nepal's Kanchenjunga Conservation Area, a melanistic leopard was photographed at an elevation of by a camera trap in May 2012.
In Sri Lanka, leopards were recorded in Yala National Park and in unprotected forest patches, tea estates, grasslands, home gardens, pine and eucalyptus plantations.
In Myanmar, leopards were recorded for the first time by camera traps in the hill forests of Myanmar's Karen State. The Northern Tenasserim Forest Complex in southern Myanmar is considered a leopard stronghold. In Thailand, leopards are present in the Western Forest Complex, Kaeng Krachan-Kui Buri, Khlong Saeng-Khao Sok protected area complexes and in Hala Bala Wildlife Sanctuary bordering Malaysia. In Peninsular Malaysia, leopards are present in Belum-Temengor, Taman Negara and Endau-Rompin National Parks.
In Laos, leopards were recorded in Nam Et-Phou Louey National Biodiversity Conservation Area and Nam Kan National Protected Area.
In Cambodia, leopards inhabit deciduous dipterocarp forest in Phnom Prich Wildlife Sanctuary and Mondulkiri Protected Forest.
In southern China, leopards were recorded only in the Qinling Mountains during surveys in 11 nature reserves between 2002 and 2009.
In Java, leopards inhabit dense tropical rainforests and dry deciduous forests at elevations from sea level to . Outside protected areas, leopards were recorded in mixed agricultural land, secondary forest and production forest between 2008 and 2014.
In the Russian Far East, it inhabits temperate coniferous forests where winter temperatures reach a low of . | Leopard | Wikipedia | 492 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
Behaviour and ecology
The leopard is a solitary and territorial animal. It is typically shy and alert when crossing roadways and encountering oncoming vehicles, but may be emboldened to attack people or other animals when threatened. Adults associate only in the mating season. Females continue to interact with their offspring even after weaning and have been observed sharing kills with their offspring when they can not obtain any prey. They produce a number of vocalizations, including growls, snarls, meows, and purrs. The roaring sequence in leopards consists mainly of grunts, also called "sawing", as it resembles the sound of sawing wood. Cubs call their mother with an urr-urr sound.
The whitish spots on the back of its ears are thought to play a role in communication.
It has been hypothesized that the white tips of their tails may function as a 'follow-me' signal in intraspecific communication. However, no significant association were found between a conspicuous colour of tail patches and behavioural variables in carnivores.
Leopards are mainly active from dusk till dawn and will rest for most of the day and some hours at night in thickets, among rocks or over tree branches. Leopards have been observed walking across their range at night; wandering up to if disturbed. In some regions, they are nocturnal. In western African forests, they have been observed to be largely diurnal and hunting during twilight, when their prey animals are active; activity patterns vary between seasons.
Leopards can climb trees quite skillfully, often resting on tree branches and descending headfirst.
They can run at over , leap over horizontally, and jump up to vertically.
Social spacing
In Kruger National Park, most leopards tend to keep apart. Males occasionally interact with their partners and cubs, and exceptionally this can extend beyond to two generations. Aggressive encounters are rare, typically limited to defending territories from intruders. In a South African reserve, a male was wounded in a male–male territorial battle over a carcass. | Leopard | Wikipedia | 419 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
Males occupy home ranges that often overlap with a few smaller female home ranges, probably as a strategy to enhance access to females. In the Ivory Coast, the home range of a female was completely enclosed within a male's. Females live with their cubs in home ranges that overlap extensively, probably due to the association between mothers and their offspring. There may be a few other fluctuating home ranges belonging to young individuals. It is not clear if male home ranges overlap as much as those of females do. Individuals try to drive away intruders of the same sex.
A study of leopards in the Namibian farmlands showed that the size of home ranges was not significantly affected by sex, rainfall patterns or season; the higher the prey availability in an area, the greater the leopard population density and the smaller the size of home ranges, but they tend to expand if there is human interference.
Sizes of home ranges vary geographically and depending on habitat and availability of prey. In the Serengeti, males have home ranges of and females of ; but males in northeastern Namibia of and females of . They are even larger in arid and montane areas. In Nepal's Bardia National Park, male home ranges of and female ones of are smaller than those generally observed in Africa.
Hunting and diet
The leopard is a carnivore that prefers medium-sized prey with a body mass ranging from . Prey species in this weight range tend to occur in dense habitat and to form small herds. Species that prefer open areas and have well-developed anti-predator strategies are less preferred. More than 100 prey species have been recorded. The most preferred species are ungulates, such as impala, bushbuck, common duiker and chital. Primates preyed upon include white-eyelid mangabeys, guenons and gray langurs. Leopards also kill smaller carnivores like black-backed jackal, bat-eared fox, genet and cheetah. In urban environments, domestic dogs provide an important food source. The largest prey killed by a leopard was reportedly a male eland weighing . A study in Wolong National Nature Reserve in southern China demonstrated variation in the leopard's diet over time; over the course of seven years, the vegetative cover receded, and leopards opportunistically shifted from primarily consuming tufted deer to pursuing bamboo rats and other smaller prey. | Leopard | Wikipedia | 487 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
The leopard depends mainly on its acute senses of hearing and vision for hunting. It primarily hunts at night in most areas. In western African forests and Tsavo National Park, they have also been observed hunting by day. They usually hunt on the ground. In the Serengeti, they have been seen to ambush prey by descending on it from trees. It stalks its prey and tries to approach as closely as possible, typically within of the target, and, finally, pounces on it and kills it by suffocation. It kills small prey with a bite to the back of the neck, but holds larger animals by the throat and strangles them. It caches kills up to apart. It is able to take large prey due to its powerful jaw muscles, and is therefore strong enough to drag carcasses heavier than itself up into trees; an individual was seen to haul a young giraffe weighing nearly up into a tree. It eats small prey immediately, but drags larger carcasses over several hundred metres and caches it safely in trees, bushes or even caves; this behaviour allows the leopard to store its prey away from rivals, and offers it an advantage over them. The way it stores the kill depends on local topography and individual preferences, varying from trees in Kruger National Park to bushes in the plain terrain of the Kalahari.
Average daily consumption rates of were estimated for males and of for females. In the southern Kalahari Desert, leopards meet their water requirements by the bodily fluids of prey and succulent plants; they drink water every two to three days and feed infrequently on moisture-rich plants such as gemsbok cucumbers, watermelon and Kalahari sour grass. | Leopard | Wikipedia | 351 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
Enemies and competitors
Across its range, the leopard coexists with a number of other large predators. In Africa, it is part of a large predator guild with lions, cheetahs, spotted and brown hyenas, and African wild dogs. The leopard is dominant only over the cheetah while the others have the advantage of size, pack numbers or both. Lions pose a great mortal threat and can be responsible for 22% of leopard deaths in Sabi Sand Game Reserve. Spotted hyenas are less threatening but are more likely to steal kills, being the culprits of up to 50% of stolen leopard kills in the same area. To counter this, leopards store their kills in the trees and out of reach. Lions have a high success rate in fetching leopard kills from trees. Leopards do not seem to actively avoid their competitors but rather difference in prey and habitat preferences appear to limit their spatial overlap. In particular, leopards use heavy vegetation regardless of whether lions are present in an area and both cats are active at the same time of day.
In Asia, the leopard's main competitors are tigers and dholes. Both the larger tiger and pack-living dhole dominate leopards during encounters. Interactions between the three predators involve chasing, stealing kills and direct killing. Tigers appear to inhabit the deep parts of the forest while leopards and dholes are pushed closer to the fringes. The three predators coexist by hunting different sized prey. In Nagarhole National Park, the average size for a leopard kill was compared to for tigers and for dholes. At Kui Buri National Park, following a reduction in prey numbers, tigers continued to feed on favoured prey while leopards and dholes had to increase their consumption of small prey. Leopards can live successfully in tiger habitat when there is abundant food and vegetation cover. Otherwise, they appear to be less common where tigers are numerous. The recovery of the tiger population in Rajaji National Park during the 2000s led to a reduction in leopard population densities.
Reproduction and life cycle | Leopard | Wikipedia | 416 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
In some areas, leopards mate all year round. In Manchuria and Siberia, they mate during January and February. On average, females begin to breed between the ages of 2½ and three, and males between the ages of two and three. The female's estrous cycle lasts about 46 days, and she is usually in heat for 6–7 days. Gestation lasts for 90 to 105 days. Cubs are usually born in a litter of 2–4 cubs. The mortality rate of cubs is estimated at 41–50% during the first year. Predators are the biggest cause for leopard cub mortality during their first year. Male leopards are known to cause infanticide, in order to bring the female back into heat. Intervals between births average 15 to 24 months, but can be shorter, depending on the survival of the cubs.
Females give birth in a cave, crevice among boulders, hollow tree or thicket. Newborn cubs weigh , and are born with closed eyes, which open four to nine days after birth. The fur of the young tends to be longer and thicker than that of adults. Their pelage is also more gray in colour with less defined spots. They begin to eat meat at around nine weeks. Around three months of age, the young begin to follow the mother on hunts. At one year of age, cubs can probably fend for themselves, but will remain with the mother for 18–24 months. After separating from their mother, sibling cubs may travel together for months. Both male and female leopards typically reach sexual maturity at 2–2⅓ years.
The generation length of the leopard is 9.3 years.
The average life span of a leopard is 12–17 years.
The oldest leopard was a captive female that died at the age of 24 years, 2 months and 13 days.
Conservation
The leopard is listed on CITES Appendix I, and hunting is banned in Botswana and Afghanistan; in 11 sub-Saharan countries, trade is restricted to skins and body parts of 2,560 individuals.
In 2007, a leopard reintroduction programme was initiated in the Russian Caucasus, where captive bred individuals are reared and trained in large enclosures in Sochi National Park; six individuals released into Caucasus Nature Reserve and Alaniya National Park in 2018 survived as of February 2022. | Leopard | Wikipedia | 463 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
Threats
The leopard is primarily threatened by habitat fragmentation and conversion of forest to agriculturally used land, which lead to a declining natural prey base, human–wildlife conflict with livestock herders and high leopard mortality rates. It is also threatened by trophy hunting and poaching. Contemporary records suggest that the leopard occurs in only 25% of its historical range.
Between 2002 and 2012, at least four leopards were estimated to have been poached per week in India for the illegal wildlife trade of its skins and bones.
In spring 2013, 37 leopard skins were found during a 7-week long market survey in major Moroccan cities. In 2014, 43 leopard skins were detected during two surveys in Morocco. Vendors admitted to have imported skins from sub-Saharan Africa.
Surveys in the Central African Republic's Chinko area revealed that the leopard population decreased from 97 individuals in 2012 to 50 individuals in 2017. In this period, transhumant pastoralists from the border area with Sudan moved in the area with their livestock. Rangers confiscated large amounts of poison in the camps of livestock herders who were accompanied by armed merchants. They engaged in poaching large herbivores, sale of bushmeat and trading leopard skins in Am Dafok.
In Java, the leopard is threatened by illegal hunting and trade. Between 2011 and 2019, body parts of 51 Javan leopards were seized including six live individuals, 12 skins, 13 skulls, 20 canines and 22 claws.
Human relations
Cultural significance
Leopards have been featured in art, mythology and folklore of many countries. In Greek mythology, it was a symbol of the god Dionysus, who was depicted wearing leopard skin and using leopards as means of transportation. In one myth, the god was captured by pirates but two leopards rescued him. Numerous Roman mosaics from North African sites depict fauna now found only in tropical Africa. During the Benin Empire, the leopard was commonly represented on engravings and sculptures and was used to symbolise the power of the king or oba, since the leopard was considered the king of the forest. The Ashanti people also used the leopard as a symbol of leadership, and only the king was permitted to have a ceremonial leopard stool. Some African cultures considered the leopard to be a smarter, better hunter than the lion and harder to kill. | Leopard | Wikipedia | 465 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
In Rudyard Kipling's "How the Leopard Got His Spots", one of his Just So Stories, a leopard with no spots in the Highveld lives with his hunting partner, the Ethiopian. When they set off to the forest, the Ethiopian changed his brown skin, and the leopard painted spots on his skin. A leopard played an important role in the 1938 Hollywood film Bringing Up Baby. African chiefs, European queens, Hollywood actors and burlesque dancers wore coats made of leopard skins.
The leopard is a frequently used motif in heraldry, most commonly as passant. The heraldic leopard lacks spots and sports a mane, making it visually almost identical to the heraldic lion, and the two are often used interchangeably. Naturalistic leopard-like depictions appear on the coat of arms of Benin, Malawi, Somalia, the Democratic Republic of the Congo and Gabon, the last of which uses a black panther.
Attacks on people
The Leopard of Rudraprayag killed more than 125 people; the Panar Leopard was thought to have killed over 400 people. Both were shot by British hunter Jim Corbett. The spotted devil of Gummalapur killed about 42 people in Karnataka, India.
In captivity
The ancient Romans kept leopards in captivity to be slaughtered in hunts as well as execute criminals. In Benin, leopards were kept and paraded as mascots, totems and sacrifices to deities. Several leopards were kept in a menagerie originally established by King John of England at the Tower of London in the 13th century; around 1235, three of these animals were given to Henry III by Holy Roman Emperor Frederick II. In modern times, leopards have been trained and tamed in circuses. | Leopard | Wikipedia | 346 | 44303 | https://en.wikipedia.org/wiki/Leopard | Biology and health sciences | Carnivora | null |
The Papanicolaou test (abbreviated as Pap test, also known as Pap smear (AE), cervical smear (BE), cervical screening (BE), or smear test (BE)) is a method of cervical screening used to detect potentially precancerous and cancerous processes in the cervix (opening of the uterus or womb) or, more rarely, anus (in both men and women). Abnormal findings are often followed up by more sensitive diagnostic procedures and, if warranted, interventions that aim to prevent progression to cervical cancer. The test was independently invented in the 1920s by the Greek physician Georgios Papanikolaou and named after him. A simplified version of the test was introduced by the Canadian obstetrician Anna Marion Hilliard in 1957.
A Pap smear is performed by opening the vagina with a speculum and collecting cells at the outer opening of the cervix at the transformation zone (where the outer squamous cervical cells meet the inner glandular endocervical cells), using an Ayre spatula or a cytobrush. The collected cells are examined under a microscope to look for abnormalities. The test aims to detect potentially precancerous changes (called cervical intraepithelial neoplasia (CIN) or cervical dysplasia; the squamous intraepithelial lesion system (SIL) is also used to describe abnormalities) caused by human papillomavirus, a sexually transmitted DNA virus. The test remains an effective, widely used method for early detection of precancer and cervical cancer. While the test may also detect infections and abnormalities in the endocervix and endometrium, it is not designed to do so. | Pap test | Wikipedia | 364 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
Guidelines on when to begin Pap smear screening are varied, but usually begin in adulthood. Guidelines on frequency vary from every three to five years. If results are abnormal, and depending on the nature of the abnormality, the test may need to be repeated in six to twelve months. If the abnormality requires closer scrutiny, the patient may be referred for detailed inspection of the cervix by colposcopy, which magnifies the view of the cervix, vagina and vulva surfaces. The person may also be referred for HPV DNA testing, which can serve as an adjunct to Pap testing. In some countries, viral DNA is checked for first, before checking for abnormal cells. Additional biomarkers that may be applied as ancillary tests with the Pap test are evolving.
Medical uses
Screening guidelines vary from country to country. In general, screening starts about the age of 20 or 25 and continues until about the age of 50 or 60. Screening is typically recommended every three to five years, as long as results are normal.
American Congress of Obstetricians and Gynecologists (ACOG) and others recommend starting screening at age 21. Many other countries wait until age 25 or later to start screening. For instance, some parts of Great Britain start screening at age 25. ACOG's general recommendation is that people with female reproductive organs age 30–65 have an annual well-woman examination, that they not get annual Pap tests, and that they do get Pap tests at three to five year intervals.
HPV is passed through skin to skin contact; sex does not have to occur, although it is a common way for it to spread. It takes an average of a year, but can take up to four years, for a person's immune system to clear the initial infection. Screening during this period may show this immune reaction and repair as mild abnormalities, which are usually not associated with cervical cancer, but could cause the patient stress and result in further tests and possible treatment. Cervical cancer usually takes time to develop, so delaying the start of screening a few years poses little risk of missing a potentially precancerous lesion. For instance, screening people under age 25 does not decrease cancer rates under age 30.
HPV can be transmitted in sex between females, so those who have only had sex with other females should be screened, although they are at somewhat lower risk for cervical cancer. | Pap test | Wikipedia | 498 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
Guidelines on frequency of screening vary—typically every three to five years for those who have not had previous abnormal smears. Some older recommendations suggested screening as frequently as every one to two years, however there is little evidence to support such frequent screening; annual screening has little benefit but leads to greatly increased cost and many unnecessary procedures and treatments. It has been acknowledged since before 1980 that most people can be screened less often. In some guidelines, frequency depends on age; for instance in Great Britain, screening is recommended every three years for women under 50, and every five years for those over.
Screening should stop at about age 65 unless there is a history of abnormal test result or disease. There is probably no benefit in screening people aged 60 or over whose previous tests have been negative. If a woman's last three Pap results were normal, she can discontinue testing at age 65, according to the USPSTF, ACOG, ACS, and ASCP; England's NHS says 64. There is no need to continue screening after a complete hysterectomy for benign disease.
Pap smear screening is still recommended for those who have been vaccinated against HPV since the vaccines do not cover all HPV types that can cause cervical cancer. Also, the vaccine does not protect against HPV exposure before vaccination.
Those with a history of endometrial cancer should discontinue routine Pap tests after hysterectomy. Further tests are unlikely to detect recurrence of cancer but do bring the risk of giving false positive results, which would lead to unnecessary further testing.
More frequent Pap smears may be needed to follow up after an abnormal Pap smear, after treatment for abnormal Pap or biopsy results, or after treatment of cancer (cervical, anal, etc.).
Effectiveness
The Pap test, when combined with a regular program of screening and appropriate follow-up, can reduce cervical cancer deaths by up to 80%. | Pap test | Wikipedia | 405 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
Failure of prevention of cancer by the Pap test can occur for many reasons, including not getting regular screening, lack of appropriate follow-up of abnormal results, and sampling and interpretation errors. In the US, over half of all invasive cancers occur in females who have never had a Pap smear; an additional 10 to 20% of cancers occur in those who have not had a Pap smear in the preceding five years. About one-quarter of US cervical cancers were in people who had an abnormal Pap smear but did not get appropriate follow-up (patient did not return for care, or clinician did not perform recommended tests or treatment).
Adenocarcinoma of the cervix has not been shown to be prevented by Pap smears. In the UK, which has a Pap smear screening program, adenocarcinoma accounts for about 15% of all cervical cancers.
Estimates of the effectiveness of the United Kingdom's call and recall system vary widely, but it may prevent about 700 deaths per year in the UK.
Multiple studies have performed sensitivity and specificity analyses on Pap smears. Sensitivity analysis captures the ability of Pap smears to correctly identify women with cervical cancer. Various studies have revealed the sensitivity of Pap smears to be between 47.19 - 55.5%. Specificity analysis captures the ability of Pap smears to correctly identify women without cervical cancer. Various studies have revealed the specificity of Pap smears to be between 64.79 - 96.8%. While Pap smears may not be entirely accurate, they remain one of the most effective cervical cancer prevention tools. Pap smears may be supplemented with HPV DNA testing.
Results
In screening a general or low-risk population, most Pap results are normal.
In the United States, about 2–3 million abnormal Pap smear results are found each year. Most abnormal results are mildly abnormal (ASC-US (typically 2–5% of Pap results) or low-grade squamous intraepithelial lesion (LSIL) (about 2% of results)), indicating HPV infection. Although most low-grade cervical dysplasias spontaneously regress without ever leading to cervical cancer, dysplasia can serve as an indication that increased vigilance is needed. | Pap test | Wikipedia | 482 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
In a typical scenario, about 0.5% of Pap results are high-grade SIL (HSIL), and less than 0.5% of results indicate cancer; 0.2 to 0.8% of results indicate Atypical Glandular Cells of Undetermined Significance (AGC-NOS).
As liquid-based preparations (LBPs) become a common medium for testing, atypical result rates have increased. The median rate for all preparations with low-grade squamous intraepithelial lesions using LBPs was 2.9% in 2006, compared with a 2003 median rate of 2.1%. Rates for high-grade squamous intraepithelial lesions (median, 0.5%) and atypical squamous cells have changed little.
Abnormal results are reported according to the Bethesda system. They include:
Atypical squamous cells (ASC)
Atypical squamous cells of undetermined significance (ASC-US)
Atypical squamous cells – cannot exclude HSIL (ASC-H)
Squamous intraepithelial lesion (SIL)
Low-grade squamous intraepithelial lesion (LGSIL or LSIL)
High-grade squamous intraepithelial lesion (HGSIL or HSIL)
Squamous cell carcinoma
Glandular epithelial cell abnormalities
Atypical glandular cells not otherwise specified (AGC or AGC-NOS)
Endocervical and endometrial abnormalities can also be detected, as can a number of infectious processes, including yeast, herpes simplex virus and trichomoniasis. However it is not very sensitive at detecting these infections, so absence of detection on a Pap does not mean absence of the infection.
Pregnancy
Pap tests can usually be performed during pregnancy up to at least 24 weeks of gestational age. Pap tests during pregnancy have not been associated with increased risk of miscarriage. An inflammatory component is commonly seen on Pap smears from pregnant women and does not appear to be a risk for subsequent preterm birth.
After childbirth, it is recommended to wait 12 weeks before taking a Pap test because inflammation of the cervix caused by the birth interferes with test interpretation. | Pap test | Wikipedia | 478 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
In transgender individuals
Transgender men are also typically at risk for HPV due to retention of the uterine cervix in the majority of individuals in this subgroup. As such, professional guidelines recommend that transgender men be screened routinely for cervical cancer using methods such as Pap smear, identical to the recommendations for cisgender women.
However, transgender men have lower rates of cervical cancer screening than cisgender women. Many transgender men report barriers to receiving gender-affirming healthcare, including lack of insurance coverage and stigma/discrimination during clinical encounters, and may encounter provider misconceptions regarding risk in this population for cervical cancer. Pap smears may be presented to patients as non-gendered screening procedures for cancer rather than one specific for examination of the female reproductive organs. Pap smears may trigger gender dysphoria in patients and gender-neutral language can be used when explaining the pathogenesis of cancer due to infection, emphasizing the pervasiveness of HPV infection regardless of gender.
Transgender women who have not had vaginoplasties are not at risk of developing cervical cancer because they do not have cervices. Transgender women who have had vaginoplasties and have a neo-cervix or neo-vagina have a small chance of developing cancer, according to the Canadian Cancer Society. Surgeons typically use penile skin to create the new vagina and cervix, which can contract HPV and lead to penile cancer, although it is considerably rarer than cervical cancer. Because the risk of this kind of cancer is so low, cervical cancer screening is not routinely offered for those with a neo-cervix. | Pap test | Wikipedia | 342 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
Procedure
According to the CDC, intercourse, douching, and the use of vaginal medicines or spermicidal foam should be avoided for 2 days before the test. A number of studies have shown that using a small amount of water-based gel lubricant does not interfere with, obscure, or distort the Pap smear. Further, cytology is not affected, nor are some STD testing. The CDC states that Pap smears can be performed during menstruation. However, the NHS recommends against cervical screening during, or in the 2 days before and after, menstruation. Pap smears can be performed during menstruation, especially if the physician is using a liquid-based test; however if bleeding is extremely heavy, endometrial cells can obscure cervical cells, and if this occurs the test may need to be repeated in 6 months.
Pap smears begin with the insertion of a speculum into the vagina, which spreads the vagina open and allows access to the cervix. The health care provider then collects a sample of cells from the outer opening or external os of the cervix by scraping it with either a spatula or brush.
Obtaining a Pap smear should not cause much pain, but may be uncomfortable. Conditions such as vaginismus, vulvodynia, or cervical stenosis can cause insertion of the speculum to be painful.
In a conventional Pap smear, the cells are placed on a glass slide and taken to the laboratory to be checked for abnormalities.
A plastic-fronded broom is sometimes used in place of the spatula or brush. The broom is not as good a collection device, since it is much less effective at collecting endocervical material than the spatula and brush. The broom is used more frequently with the advent of liquid-based cytology, although either type of collection device may be used with either type of cytology.
The sample is stained using the Papanicolaou technique, in which tinctorial dyes and acids are selectively retained by cells. Unstained cells cannot be seen adequately with a light microscope. Papanicolaou chose stains that highlighted cytoplasmic keratinization, which actually has almost nothing to do with the nuclear features used to make diagnoses now. | Pap test | Wikipedia | 483 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
A single smear has an area of 25 x 50 mm and contains a few hundred thousand cells on average. Screening with light microscopy is first done on low (10x) power and then switched to higher (40x) power upon viewing suspicious findings. Cells are analyzed under high power for morphologic changes indicative of malignancy (including enlarged and irregularly shaped nucleus, an increase in nucleus to cytoplasm ratio, and more coarse and irregular chromatin). Approximately 1,000 fields of view are required on 10x power for screening of a single sample, which takes on average 5 to 10 minutes.
In some cases, a computer system may prescreen the slides, indicating those that do not need examination by a person or highlighting areas for special attention. The sample is then usually screened by a specially trained and qualified cytotechnologist using a light microscope. The terminology for who screens the sample varies according to the country; in the UK, the personnel are known as cytoscreeners, biomedical scientists (BMS), advanced practitioners and pathologists. The latter two take responsibility for reporting the abnormal sample, which may require further investigation.
Automated analysis
In the last decade, there have been successful attempts to develop automated, computer image analysis systems for screening. Although, on the available evidence automated cervical screening could not be recommended for implementation into a national screening program, a recent NHS Health technology appraisal concluded that the 'general case for automated image analysis ha(d) probably been made'. Automation may improve sensitivity and reduce unsatisfactory specimens. Two systems have been approved by the FDA and function in high-volume reference laboratories, with human oversight.
Types of screening
Conventional Pap—In a conventional Pap smear, samples are smeared directly onto a microscope slide after collection.
Liquid-based cytology—The sample of (epithelial) cells is taken from the transitional zone, the squamocolumnar junction of the cervix, between the ectocervix and the endocervix. The cells taken are suspended in a bottle of preservative for transport to the laboratory, where they are analyzed using Pap stains. | Pap test | Wikipedia | 446 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
Pap tests commonly examine epithelial abnormalities, such as metaplasia, dysplasia, or borderline changes, all of which may be indicative of CIN. Nuclei will stain dark blue, squamous cells will stain green and keratinised cells will stain pink/ orange. Koilocytes may be observed where there is some dyskaryosis (of epithelium). The nucleus in koilocytes is typically irregular, indicating possible cause for concern; requiring further confirmatory screens and tests.
In addition, human papillomavirus (HPV) test may be performed either as indicated for abnormal Pap results, or in some cases, dual testing is done, where both a Pap smear and an HPV test are done at the same time (also called Pap co-testing).
Practical aspects
The endocervix may be partially sampled with the device used to obtain the ectocervical sample, but due to the anatomy of this area, consistent and reliable sampling cannot be guaranteed. Since abnormal endocervical cells may be sampled, those examining them are taught to recognize them.
The endometrium is not directly sampled with the device used to sample the ectocervix. Cells may exfoliate onto the cervix and be collected from there, so as with endocervical cells, abnormal cells can be recognised if present but the Pap test should not be used as a screening tool for endometrial malignancy.
In the United States, a Pap test itself costs $20 to $30, but the costs for Pap test visits can cost over $1,000, largely because additional tests are added that may or may not be necessary.
History
The test was invented by and named after the Greek doctor Georgios Papanikolaou, who started his research in 1923. Aurel Babeș independently made similar discoveries in 1927. However, Babeș' method was radically different from Papanikolaou's. | Pap test | Wikipedia | 415 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
The Pap test was finally recognized only after a leading article in the American Journal of Obstetrics and Gynecology in 1941 by Papanikolaou and Herbert F. Traut, an American gynecologist. A monograph titled Diagnosis of Uterine Cancer by the Vaginal Smear that they published contained drawings of the various cells seen in patients with no disease, inflammatory conditions, and preclinical and clinical carcinoma. The monograph was illustrated by Hashime Murayama, who later became a staff illustrator with the National Geographic Society. Both Papanikolaou and his wife, Andromachi Papanikolaou, dedicated the rest of their lives to teaching the technique to other physicians and laboratory personnel.
Experimental techniques
In the developed world, cervical biopsy guided by colposcopy is considered the "gold standard" for diagnosing cervical abnormalities after an abnormal Pap smear. Other techniques such as triple smear are also done after an abnormal Pap smear. The procedure requires a trained colposcopist and can be expensive to perform. However, Pap smears are very sensitive and some negative biopsy results may represent undersampling of the lesion in the biopsy, so negative biopsy with positive cytology requires careful follow-up.
Experimental visualization techniques use broad-band light (e.g., direct visualization, speculoscopy, cervicography, visual inspection with acetic acid or with Lugol's, and colposcopy) and electronic detection methods (e.g., Polarprobe and in vivo spectroscopy). These techniques are less expensive and can be performed with significantly less training. They do not perform as well as Pap smear screening and colposcopy. At this point, these techniques have not been validated by large-scale trials and are not in general use.
Implementation by country
Australia
Australia has used the Pap test as part of its cervical screening program since its implementation in 1991 which required women past the age of 18 be tested every two years. In December 2017 Australia discontinued its use of the Pap test and replaced it with a new HPV test that is only required to be conducted once every five years from the age of 25. Medicare covers the costs of testing; however, if a patient's doctor does not allow bulk billing, they may have to pay for the appointment and then claim the Medicare rebate. | Pap test | Wikipedia | 496 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
Taiwan
Free Pap tests were offered from 1974–1984 before being replaced by a system in which all women over the age of 30 could have the cost of their Pap test reimbursed by the National Health Insurance in 1995. This policy was still ongoing in 2018 and encouraged women to screen at least every three years.
Despite this, the number of people receiving Pap tests remain lower than countries like Australia. Some believe this is due to a lack of awareness regarding the test and its availability. It has also been found that women who have chronic diseases or other reproductive diseases are less likely to receive the test.
England
the NHS maintains a cervical screening program in which women between the age of 25–49 are invited for a smear test every three years, and women past 50 every five years. Much like Australia, England uses a HPV test before examining cells that test positive using the Pap test. The test is free as part of the national cervical screening program.
Coccoid bacteria
The finding of coccoid bacteria on a Pap test is of no consequence with otherwise normal test findings and no infectious symptoms. However, if there is enough inflammation to obscure the detection of precancerous and cancerous processes, it may indicate treatment with a broad-spectrum antibiotic for streptococci and anaerobic bacteria (such as metronidazole and amoxicillin) before repeating the smear. Alternatively, the test will be repeated at an earlier time than it would otherwise. If there are symptoms of vaginal discharge, bad odor or irritation, the presence of coccoid bacteria also may indicate treatment with antibiotics as per above. | Pap test | Wikipedia | 335 | 44305 | https://en.wikipedia.org/wiki/Pap%20test | Biology and health sciences | Medical procedures | null |
An invention is a unique or novel device, method, composition, idea or process. An invention may be an improvement upon a machine, product, or process for increasing efficiency or lowering cost. It may also be an entirely new concept. If an idea is unique enough either as a stand-alone invention or as a significant improvement over the work of others, it can be patented. A patent, if granted, gives the inventor a proprietary interest in the patent over a specific period of time, which can be licensed for financial gain.
An inventor creates or discovers an invention. The word inventor comes from the Latin verb invenire, invent-, to find. Although inventing is closely associated with science and engineering, inventors are not necessarily engineers or scientists. Due to advances in artificial intelligence, the term "inventor" no longer exclusively applies to an occupation (see human computers).
Some inventions can be patented. The system of patents was established to encourage inventors by granting limited-term, limited monopoly on inventions determined to be sufficiently novel, non-obvious, and useful. A patent legally protects the intellectual property rights of the inventor and legally recognizes that a claimed invention is actually an invention. The rules and requirements for patenting an invention vary by country and the process of obtaining a patent is often expensive.
Another meaning of invention is cultural invention, which is an innovative set of useful social behaviours adopted by people and passed on to others. The Institute for Social Inventions collected many such ideas in magazines and books. Invention is also an important component of artistic and design creativity. Inventions often extend the boundaries of human knowledge, experience or capability.
Types
Inventions are of three kinds: scientific-technological (including medicine), sociopolitical (including economics and law), and humanistic, or cultural.
Scientific-technological inventions include railroads, aviation, vaccination, hybridization, antibiotics, astronautics, holography, the atomic bomb, computing, the Internet, and the smartphone.
Sociopolitical inventions comprise new laws, institutions, and procedures that change modes of social behavior and establish new forms of human interaction and organization. Examples include the British Parliament, the US Constitution, the Manchester (UK) General Union of Trades, the Boy Scouts, the Red Cross, the Olympic Games, the United Nations, the European Union, and the Universal Declaration of Human Rights, as well as movements such as socialism, Zionism, suffragism, feminism, and animal-rights veganism. | Invention | Wikipedia | 500 | 44312 | https://en.wikipedia.org/wiki/Invention | Technology | Technology: General | null |
Humanistic inventions encompass culture in its entirety and are as transformative and important as any in the sciences, although people tend to take them for granted. In the domain of linguistics, for example, many alphabets have been inventions, as are all neologisms (Shakespeare invented about 1,700 words). Literary inventions include the epic, tragedy, comedy, the novel, the sonnet, the Renaissance, neoclassicism, Romanticism, Symbolism, Aestheticism, Socialist Realism, Surrealism, postmodernism, and (according to Freud) psychoanalysis. Among the inventions of artists and musicians are oil painting, printmaking, photography, cinema, musical tonality, atonality, jazz, rock, opera, and the symphony orchestra. Philosophers have invented logic (several times), dialectics, idealism, materialism, utopia, anarchism, semiotics, phenomenology, behaviorism, positivism, pragmatism, and deconstruction. Religious thinkers are responsible for such inventions as monotheism, pantheism, Methodism, Mormonism, iconoclasm, puritanism, deism, secularism, ecumenism, and the Baháʼí Faith. Some of these disciplines, genres, and trends may seem to have existed eternally or to have emerged spontaneously of their own accord, but most of them have had inventors.
Process
Practical means
Ideas for an invention may be developed on paper or on a computer, by writing or drawing, by trial and error, by making models, by experimenting, by testing and/or by making the invention in its whole form. Brainstorming also can spark new ideas for an invention. Collaborative creative processes are frequently used by engineers, designers, architects and scientists. Co-inventors are frequently named on patents.
In addition, many inventors keep records of their working process – notebooks, photos, etc., including Leonardo da Vinci, Galileo Galilei, Evangelista Torricelli, Thomas Jefferson and Albert Einstein.
In the process of developing an invention, the initial idea may change. The invention may become simpler, more practical, it may expand, or it may even morph into something totally different. Working on one invention can lead to others too.
History shows that turning the concept of an invention into a working device is not always swift or direct. Inventions may also become more useful after time passes and other changes occur. For example, the parachute became more useful once powered flight was a reality. | Invention | Wikipedia | 511 | 44312 | https://en.wikipedia.org/wiki/Invention | Technology | Technology: General | null |
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